feat: add ZFS monitoring (#2209)

- track pool capacity, health, I/O, scrub status, and vdev errors
- report dataset usage and correct ZFS filesystem metrics
- add pool charts, detail views, refresh controls, and health alerts
- persist pool details and include ZFS usage in disk alerts
- support configurable detail intervals and legacy agent compatibility

---------

Co-authored-by: hank <hank@henrygd.me>

agent/agent.go

@@ -48,6 +48,7 @@ type Agent struct {
 	keys                      []gossh.PublicKey                                     // SSH public keys
 	smartManager              *SmartManager                                         // Manages SMART data
 	systemdManager            *systemdManager                                       // Manages systemd services
+	zfsManager                *ZfsManager                                           // Manages ZFS pool and dataset data
 }
 
 // NewAgent creates a new agent with the given data directory for persisting data.
@@ -121,6 +122,19 @@ func NewAgent(dataDir ...string) (agent *Agent, err error) {
 	// initialize handler registry
 	agent.handlerRegistry = NewHandlerRegistry()
 
+	agent.zfsManager = newZfsManager()
+
+	// ZFS_INTERVAL env var to update ZFS detail data at this interval
+	if zfsIntervalEnv, exists := utils.GetEnv("ZFS_INTERVAL"); exists {
+		if duration, err := time.ParseDuration(zfsIntervalEnv); err == nil && duration > 0 {
+			agent.zfsManager.detailInterval = duration
+			agent.systemDetails.ZfsInterval = duration
+			slog.Info("ZFS_INTERVAL", "duration", duration)
+		} else {
+			slog.Warn("Invalid ZFS_INTERVAL", "err", err)
+		}
+	}
+
 	// initialize disk info
 	agent.initializeDiskInfo()
 

agent/disk.go

@@ -537,7 +537,16 @@ func normalizeDeviceName(value string) string {
 func (a *Agent) initializeDiskIoStats(diskIoCounters map[string]disk.IOCountersStat) {
 	a.fsNames = a.fsNames[:0]
 	now := time.Now()
+	// ZFS datasets have no /proc/diskstats entry, so they are excluded from
+	// I/O tracking instead of warning about a missing device (#1541).
+	var zfsMountpoints map[string]bool
+	if a.zfsManager != nil {
+		zfsMountpoints = a.zfsManager.ZfsMountpoints()
+	}
 	for device, stats := range a.fsStats {
+		if zfsMountpoints[stats.Mountpoint] {
+			continue
+		}
 		// skip if not in diskIoCounters
 		d, exists := diskIoCounters[device]
 		if !exists {
@@ -562,20 +571,31 @@ func (a *Agent) updateDiskUsage(systemStats *system.Stats) {
 		!a.lastDiskUsageUpdate.IsZero() &&
 		time.Since(a.lastDiskUsageUpdate) < a.diskUsageCacheDuration
 
+	// ZFS dataset mountpoints use `zfs list` values because statfs(2) reports
+	// dataset-level usage that excludes child datasets (#1541).
+	var zfsUsage map[string]zfsDatasetUsage
+	if a.zfsManager != nil {
+		zfsUsage = a.zfsManager.DatasetUsage()
+	}
+
 	// disk usage
 	for _, stats := range a.fsStats {
 		// Skip non-root filesystems if caching is active
 		if cacheExtraFs && !stats.Root {
 			continue
 		}
-		if d, err := disk.Usage(stats.Mountpoint); err == nil {
-			stats.DiskTotal = utils.BytesToGigabytes(d.Total)
-			stats.DiskUsed = utils.BytesToGigabytes(d.Used)
-			if stats.Root {
-				systemStats.DiskTotal = utils.BytesToGigabytes(d.Total)
-				systemStats.DiskUsed = utils.BytesToGigabytes(d.Used)
-				systemStats.DiskPct = utils.TwoDecimals(d.UsedPercent)
+		var total, used uint64
+		var usedPct float64
+		if u, ok := zfsUsage[stats.Mountpoint]; ok {
+			total = u.used + u.avail
+			used = u.used
+			if total > 0 {
+				usedPct = float64(used) / float64(total) * 100
 			}
+		} else if d, err := disk.Usage(stats.Mountpoint); err == nil {
+			total = d.Total
+			used = d.Used
+			usedPct = d.UsedPercent
 		} else {
 			// reset stats if error (likely unmounted)
 			slog.Error("Error getting disk stats", "name", stats.Mountpoint, "err", err)
@@ -583,6 +603,14 @@ func (a *Agent) updateDiskUsage(systemStats *system.Stats) {
 			stats.DiskUsed = 0
 			stats.TotalRead = 0
 			stats.TotalWrite = 0
+			continue
+		}
+		stats.DiskTotal = utils.BytesToGigabytes(total)
+		stats.DiskUsed = utils.BytesToGigabytes(used)
+		if stats.Root {
+			systemStats.DiskTotal = stats.DiskTotal
+			systemStats.DiskUsed = stats.DiskUsed
+			systemStats.DiskPct = utils.TwoDecimals(usedPct)
 		}
 	}
 

agent/disk_zfs_test.go

@@ -0,0 +1,109 @@
+//go:build testing
+
+package agent
+
+import (
+	"testing"
+
+	"github.com/henrygd/beszel/agent/zfs"
+	"github.com/henrygd/beszel/internal/entities/system"
+	"github.com/shirou/gopsutil/v4/disk"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestUpdateDiskUsageZfsMountpoint verifies that a filesystem whose mountpoint
+// is a ZFS dataset reports `zfs list` usage (which includes child datasets)
+// instead of the dataset-scoped statfs values (#1541).
+func TestUpdateDiskUsageZfsMountpoint(t *testing.T) {
+	zm := &ZfsManager{}
+	zm.datasetsFn = func() ([]zfs.Dataset, error) {
+		return []zfs.Dataset{
+			{Name: "tank", Used: 12000000000000, Avail: 11999000000000, Mountpoint: "/tank"},
+		}, nil
+	}
+	agent := &Agent{
+		fsStats: map[string]*system.FsStats{
+			"tank": {Root: false, Mountpoint: "/tank"},
+		},
+		zfsManager: zm,
+	}
+
+	var stats system.Stats
+	agent.updateDiskUsage(&stats)
+
+	fs := agent.fsStats["tank"]
+	require.NotNil(t, fs)
+	assert.Equal(t, 22350.81, fs.DiskTotal) // (used + avail) in GiB
+	assert.Equal(t, 11175.87, fs.DiskUsed)
+	// Non-root filesystems do not populate system-level stats.
+	assert.Equal(t, float64(0), stats.DiskTotal)
+}
+
+// TestUpdateDiskUsageZfsRootPopulatesSystemStats verifies the root disk values
+// are derived from ZFS usage when the root mountpoint is a ZFS dataset.
+func TestUpdateDiskUsageZfsRootPopulatesSystemStats(t *testing.T) {
+	zm := &ZfsManager{}
+	zm.datasetsFn = func() ([]zfs.Dataset, error) {
+		return []zfs.Dataset{
+			{Name: "rpool/ROOT/pve-1", Used: 900000000000, Avail: 300000000000, Mountpoint: "/"},
+		}, nil
+	}
+	agent := &Agent{
+		fsStats: map[string]*system.FsStats{
+			"rpool/ROOT/pve-1": {Root: true, Mountpoint: "/"},
+		},
+		zfsManager: zm,
+	}
+
+	var stats system.Stats
+	agent.updateDiskUsage(&stats)
+
+	assert.Equal(t, 1117.59, agent.fsStats["rpool/ROOT/pve-1"].DiskTotal)
+	assert.Equal(t, 838.19, agent.fsStats["rpool/ROOT/pve-1"].DiskUsed)
+	assert.Equal(t, 75.0, stats.DiskPct)
+	assert.Equal(t, 1117.59, stats.DiskTotal)
+	assert.Equal(t, 838.19, stats.DiskUsed)
+}
+
+// TestUpdateDiskUsageWithoutZfsManager falls back to statfs when no manager is
+// present (e.g. tests constructing bare Agent values).
+func TestUpdateDiskUsageWithoutZfsManager(t *testing.T) {
+	agent := &Agent{
+		fsStats: map[string]*system.FsStats{
+			"root": {Root: true, Mountpoint: "/"},
+		},
+	}
+
+	var stats system.Stats
+	agent.updateDiskUsage(&stats)
+
+	assert.True(t, agent.fsStats["root"].DiskTotal > 0, "root usage should come from statfs")
+	assert.True(t, stats.DiskTotal > 0)
+}
+
+// TestInitializeDiskIoStatsSkipsZfsMountpoints verifies ZFS filesystems are
+// excluded from diskstats I/O tracking instead of warning about a missing device.
+func TestInitializeDiskIoStatsSkipsZfsMountpoints(t *testing.T) {
+	zm := &ZfsManager{}
+	zm.datasetsFn = func() ([]zfs.Dataset, error) {
+		return []zfs.Dataset{{Name: "tank", Mountpoint: "/tank"}}, nil
+	}
+	agent := &Agent{
+		fsStats: map[string]*system.FsStats{
+			"tank": {Root: false, Mountpoint: "/tank"},
+			"sda1": {Root: false, Mountpoint: "/mnt/data"},
+		},
+		zfsManager: zm,
+		diskPrev:   make(map[uint16]map[string]prevDisk),
+	}
+
+	agent.initializeDiskIoStats(map[string]disk.IOCountersStat{
+		"sda1": {Name: "sda1", ReadBytes: 100, WriteBytes: 100},
+	})
+
+	assert.Equal(t, []string{"sda1"}, agent.fsNames)
+	assert.Equal(t, uint64(100), agent.fsStats["sda1"].TotalRead)
+	// ZFS entry is present but untouched by diskstats initialization.
+	assert.Equal(t, uint64(0), agent.fsStats["tank"].TotalRead)
+}

agent/handlers.go

@@ -51,6 +51,7 @@ func NewHandlerRegistry() *HandlerRegistry {
 	registry.Register(common.GetContainerInfo, &GetContainerInfoHandler{})
 	registry.Register(common.GetSmartData, &GetSmartDataHandler{})
 	registry.Register(common.GetSystemdInfo, &GetSystemdInfoHandler{})
+	registry.Register(common.GetZfsData, &GetZfsDataHandler{})
 
 	return registry
 }
@@ -178,6 +179,23 @@ func (h *GetSmartDataHandler) Handle(hctx *HandlerContext) error {
 	}, hctx.RequestID)
 }
 
+////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////
+
+// GetZfsDataHandler handles ZFS detail data requests
+type GetZfsDataHandler struct{}
+
+func (h *GetZfsDataHandler) Handle(hctx *HandlerContext) error {
+	if hctx.Agent.zfsManager == nil {
+		return hctx.SendResponse(nil, hctx.RequestID)
+	}
+	var req common.ZfsDataRequest
+	if err := cbor.Unmarshal(hctx.Request.Data, &req); err != nil {
+		return err
+	}
+	return hctx.SendResponse(hctx.Agent.zfsManager.GetDetail(req.Force), hctx.RequestID)
+}
+
 ////////////////////////////////////////////////////////////////////////////
 ////////////////////////////////////////////////////////////////////////////
 ////////////////////////////////////////////////////////////////////////////

agent/handlers_test.go

@@ -4,8 +4,10 @@ package agent
 
 import (
 	"testing"
+	"time"
 
 	"github.com/fxamacker/cbor/v2"
+	"github.com/henrygd/beszel/agent/zfs"
 	"github.com/henrygd/beszel/internal/common"
 	"github.com/henrygd/beszel/internal/entities/smart"
 	"github.com/stretchr/testify/assert"
@@ -30,6 +32,32 @@ func TestNewAgentResponseSmartData(t *testing.T) {
 	assert.True(t, response.SmartComplete)
 }
 
+func TestGetZfsDataHandlerForceRefresh(t *testing.T) {
+	poolCalls := 0
+	zm := &ZfsManager{detailInterval: time.Hour}
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) {
+		poolCalls++
+		return []zfs.PoolStat{{Name: "tank", Alloc: uint64(poolCalls)}}, nil
+	}
+	zm.poolStatusesFn = func() ([]zfs.PoolStatus, error) { return nil, nil }
+	zm.datasetsFn = func() ([]zfs.Dataset, error) { return nil, nil }
+	zm.GetDetail(false)
+
+	requestData, err := cbor.Marshal(common.ZfsDataRequest{Force: true})
+	assert.NoError(t, err)
+	ctx := &HandlerContext{
+		Agent: &Agent{zfsManager: zm},
+		Request: &common.HubRequest[cbor.RawMessage]{
+			Action: common.GetZfsData,
+			Data:   requestData,
+		},
+		SendResponse: func(any, *uint32) error { return nil },
+	}
+
+	assert.NoError(t, (&GetZfsDataHandler{}).Handle(ctx))
+	assert.Equal(t, 2, poolCalls)
+}
+
 func (m *MockHandler) Handle(ctx *HandlerContext) error {
 	if m.handleFunc != nil {
 		return m.handleFunc(ctx)

agent/system.go

@@ -219,6 +219,9 @@ func (a *Agent) getSystemStats(cacheTimeMs uint16) system.Stats {
 	// disk i/o (cache-aware per interval)
 	a.updateDiskIo(cacheTimeMs, &systemStats)
 
+	// zfs pool stats
+	a.zfsManager.Update(&systemStats)
+
 	// network stats (per cache interval)
 	a.updateNetworkStats(cacheTimeMs, &systemStats)
 

agent/test-data/zfs/zfs_list.txt

@@ -0,0 +1,9 @@
+tank	12000000000000	11999000000000	/tank
+tank/apps	1000000000000	11999000000000	/tank/apps
+tank/backup	2000000000000	11999000000000	/tank/backup
+tank/media	1000000000000	11999000000000	/tank/my media
+rpool	900000000000	300000000000	-
+rpool/ROOT	1000000000	300000000000	-
+rpool/ROOT/pve-1	890000000000	300000000000	/
+rpool/data	9000000000	300000000000	-
+rpool/data/subvol-100-disk-0	400000000000	300000000000	/subvol-100-disk-0

agent/test-data/zfs/zpool_list.txt

@@ -0,0 +1,2 @@
+tank	23999000000000	12000000000000	11999000000000	ONLINE
+rpool	1200000000000	900000000000	300000000000	DEGRADED

agent/test-data/zfs/zpool_status.txt

@@ -0,0 +1,29 @@
+  pool: tank
+ state: ONLINE
+  scan: scrub repaired 0B in 00:05:12 with 0 errors on Sun Jun  1 02:00:12 2025
+config:
+
+	NAME        STATE     READ WRITE CKSUM
+	tank        ONLINE       0     0     0
+	  mirror-0  ONLINE       0     0     0
+	    sda     ONLINE       0     0     0
+	    sdb     ONLINE       0     0     0
+
+errors: No known data errors
+
+  pool: rpool
+ state: DEGRADED
+ status: One or more devices could not be used because the label is missing or
+	invalid.  Sufficient replicas exist for the pool to continue functioning in a
+	degraded state.
+  scan: scrub in progress since Sun Jun  8 01:00:00 2025
+	10.00% done, 01:30:00 to go, 0.00/s
+config:
+
+	NAME        STATE     READ WRITE CKSUM
+	rpool       DEGRADED     0     0     0
+	  mirror-0  DEGRADED     0     0     0
+	    sda     ONLINE       0     0     0
+	    sdb     FAULTED      1     2     3
+
+errors: 1 data errors, use '-v' for a list

agent/zfs/zfs.go

@@ -0,0 +1,160 @@
+// Package zfs provides functions to read ZFS statistics.
+package zfs
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var commandTimeout = 10 * time.Second
+
+var commandOutput = func(name string, args ...string) ([]byte, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), commandTimeout)
+	defer cancel()
+	cmd := exec.CommandContext(ctx, name, args...)
+	cmd.Env = append(os.Environ(), "LC_ALL=C", "LANG=C")
+	out, err := cmd.Output()
+	if ctx.Err() != nil {
+		return nil, fmt.Errorf("%s timed out after %s: %w", name, commandTimeout, ctx.Err())
+	}
+	return out, err
+}
+
+// ErrNoZfs is returned when the ZFS utilities or kernel interfaces are unavailable.
+var ErrNoZfs = errors.New("zfs utilities unavailable")
+
+// PoolStat is a snapshot of a ZFS pool's capacity and health.
+type PoolStat struct {
+	Name   string
+	Size   uint64 // total capacity in bytes
+	Alloc  uint64 // allocated bytes
+	Free   uint64 // free bytes
+	Health string // ONLINE, DEGRADED, FAULTED, ...
+}
+
+// PoolKernelStat is the inexpensive pool telemetry exposed by the ZFS kernel.
+// NRead and NWrite are cumulative byte counters since the pool was imported.
+type PoolKernelStat struct {
+	Name   string
+	Health string
+	NRead  uint64
+	NWrite uint64
+}
+
+// PoolIoStats holds calculated per-second I/O rates for a pool.
+type PoolIoStats struct {
+	NRead  uint64
+	NWrite uint64
+}
+
+// Dataset is a single ZFS dataset with usage information.
+type Dataset struct {
+	Name       string
+	Used       uint64
+	Avail      uint64
+	Mountpoint string
+}
+
+// PoolStats returns capacity and health for all pools on the system using
+// `zpool list`. Frequent health and I/O sampling uses PoolKernelStats instead.
+func PoolStats() ([]PoolStat, error) {
+	out, err := commandOutput("zpool", "list", "-Hp", "-o", "name,size,alloc,free,health")
+	if err != nil {
+		var exitErr *exec.ExitError
+		if errors.As(err, &exitErr) && strings.Contains(string(exitErr.Stderr), "no pools available") {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("zpool list: %w", err)
+	}
+	return parseZpoolListOutput(out)
+}
+
+// Datasets returns all datasets on the system with usage and mountpoint
+// information using `zfs list` (recursive by default).
+func Datasets() ([]Dataset, error) {
+	out, err := commandOutput("zfs", "list", "-Hp", "-o", "name,used,avail,mountpoint")
+	if err != nil {
+		return nil, fmt.Errorf("zfs list: %w", err)
+	}
+	return parseZfsListOutput(out)
+}
+
+// parseZpoolListOutput parses `zpool list -Hp -o name,size,alloc,free,health` output.
+// Columns are tab-separated; numeric columns are raw bytes.
+func parseZpoolListOutput(out []byte) ([]PoolStat, error) {
+	var pools []PoolStat
+	scanner := bufio.NewScanner(bytes.NewReader(out))
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" {
+			continue
+		}
+		if line == "no pools available" && len(pools) == 0 {
+			return nil, nil
+		}
+		fields := strings.Split(line, "\t")
+		if len(fields) < 5 {
+			return nil, fmt.Errorf("unexpected zpool list line: %q", line)
+		}
+		size, err := strconv.ParseUint(fields[1], 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("parsing size for pool %q: %w", fields[0], err)
+		}
+		alloc, err := strconv.ParseUint(fields[2], 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("parsing alloc for pool %q: %w", fields[0], err)
+		}
+		free, err := strconv.ParseUint(fields[3], 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("parsing free for pool %q: %w", fields[0], err)
+		}
+		pools = append(pools, PoolStat{
+			Name:   fields[0],
+			Size:   size,
+			Alloc:  alloc,
+			Free:   free,
+			Health: fields[4],
+		})
+	}
+	return pools, scanner.Err()
+}
+
+// parseZfsListOutput parses `zfs list -Hp -o name,used,avail,mountpoint` output.
+// The mountpoint column may contain spaces, so it is split on tabs only.
+func parseZfsListOutput(out []byte) ([]Dataset, error) {
+	var datasets []Dataset
+	scanner := bufio.NewScanner(bytes.NewReader(out))
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" {
+			continue
+		}
+		fields := strings.SplitN(line, "\t", 4)
+		if len(fields) < 4 {
+			return nil, fmt.Errorf("unexpected zfs list line: %q", line)
+		}
+		used, err := strconv.ParseUint(fields[1], 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("parsing used for dataset %q: %w", fields[0], err)
+		}
+		avail, err := strconv.ParseUint(fields[2], 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("parsing avail for dataset %q: %w", fields[0], err)
+		}
+		datasets = append(datasets, Dataset{
+			Name:       fields[0],
+			Used:       used,
+			Avail:      avail,
+			Mountpoint: fields[3],
+		})
+	}
+	return datasets, scanner.Err()
+}

agent/zfs/zfs_freebsd.go

@@ -3,9 +3,17 @@
 package zfs
 
 import (
+	"errors"
+
 	"golang.org/x/sys/unix"
 )
 
 func ARCSize() (uint64, error) {
 	return unix.SysctlUint64("kstat.zfs.misc.arcstats.size")
 }
+
+// FreeBSD does not expose Linux's per-pool procfs kstats. Capacity, health,
+// and detail collection still work through the cached utilities.
+func PoolKernelStats() ([]PoolKernelStat, error) {
+	return nil, errors.ErrUnsupported
+}

agent/zfs/zfs_linux.go

@@ -5,14 +5,18 @@ package zfs
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"os"
+	"path/filepath"
 	"strconv"
 	"strings"
 )
 
+var procZfsPath = "/proc/spl/kstat/zfs"
+
 func ARCSize() (uint64, error) {
-	file, err := os.Open("/proc/spl/kstat/zfs/arcstats")
+	file, err := os.Open(filepath.Join(procZfsPath, "arcstats"))
 	if err != nil {
 		return 0, err
 	}
@@ -29,6 +33,167 @@ func ARCSize() (uint64, error) {
 			return strconv.ParseUint(fields[2], 10, 64)
 		}
 	}
+	if err := scanner.Err(); err != nil {
+		return 0, err
+	}
 
 	return 0, fmt.Errorf("size field not found in arcstats")
 }
+
+// PoolKernelStats reads pool state and cumulative I/O counters directly from
+// procfs. These kstats are the same interfaces used by node_exporter's Linux
+// ZFS collector and avoid keeping a `zpool iostat` subprocess alive.
+func PoolKernelStats() ([]PoolKernelStat, error) {
+	poolDirs := make(map[string]struct{})
+	for _, filename := range []string{"state", "io", "objset-*"} {
+		paths, err := filepath.Glob(filepath.Join(procZfsPath, "*", filename))
+		if err != nil {
+			return nil, err
+		}
+		for _, path := range paths {
+			poolDirs[filepath.Dir(path)] = struct{}{}
+		}
+	}
+	if len(poolDirs) == 0 {
+		return nil, ErrNoZfs
+	}
+	pools := make([]PoolKernelStat, 0, len(poolDirs))
+	for poolDir := range poolDirs {
+		nread, nwrite, err := readPoolCounters(poolDir)
+		if err != nil {
+			if errors.Is(err, os.ErrNotExist) {
+				continue // pool may have been exported after the glob
+			}
+			return nil, err
+		}
+		state, err := os.ReadFile(filepath.Join(poolDir, "state"))
+		if err != nil && !errors.Is(err, os.ErrNotExist) {
+			return nil, err
+		}
+		pools = append(pools, PoolKernelStat{
+			Name: filepath.Base(poolDir), Health: strings.ToUpper(strings.TrimSpace(string(state))),
+			NRead: nread, NWrite: nwrite,
+		})
+	}
+	if len(pools) == 0 {
+		return nil, ErrNoZfs
+	}
+	return pools, nil
+}
+
+// readPoolCounters supports both ZFS kernel interfaces. OpenZFS through 2.3
+// exposes aggregate vdev counters in "io". When that file is unavailable, sum
+// the logical I/O counters exposed for each dataset in the pool.
+func readPoolCounters(poolDir string) (uint64, uint64, error) {
+	nread, nwrite, err := readPoolIO(filepath.Join(poolDir, "io"))
+	if err == nil || !errors.Is(err, os.ErrNotExist) {
+		return nread, nwrite, err
+	}
+	return readPoolObjsets(poolDir)
+}
+
+func readPoolIO(path string) (uint64, uint64, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return 0, 0, err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) < 2 || fields[0] != "nread" {
+			continue
+		}
+		if !scanner.Scan() {
+			break
+		}
+		values := strings.Fields(scanner.Text())
+		if len(values) < 2 {
+			break
+		}
+		nread, err := strconv.ParseUint(values[0], 10, 64)
+		if err != nil {
+			return 0, 0, fmt.Errorf("parsing nread in %s: %w", path, err)
+		}
+		nwrite, err := strconv.ParseUint(values[1], 10, 64)
+		if err != nil {
+			return 0, 0, fmt.Errorf("parsing nwritten in %s: %w", path, err)
+		}
+		return nread, nwrite, nil
+	}
+	if err := scanner.Err(); err != nil {
+		return 0, 0, err
+	}
+	return 0, 0, fmt.Errorf("I/O counters not found in %s", path)
+}
+
+func readPoolObjsets(poolDir string) (uint64, uint64, error) {
+	paths, err := filepath.Glob(filepath.Join(poolDir, "objset-*"))
+	if err != nil {
+		return 0, 0, err
+	}
+	if len(paths) == 0 {
+		return 0, 0, fmt.Errorf("dataset I/O counters not found in %s", poolDir)
+	}
+
+	var totalRead, totalWrite uint64
+	objsetsRead := 0
+	for _, path := range paths {
+		nread, nwrite, err := readObjsetIO(path)
+		if errors.Is(err, os.ErrNotExist) {
+			continue // dataset may have been destroyed after the glob
+		}
+		if err != nil {
+			return 0, 0, err
+		}
+		totalRead += nread
+		totalWrite += nwrite
+		objsetsRead++
+	}
+	if objsetsRead == 0 {
+		return 0, 0, fmt.Errorf("dataset I/O counters not found in %s", poolDir)
+	}
+	return totalRead, totalWrite, nil
+}
+
+func readObjsetIO(path string) (uint64, uint64, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return 0, 0, err
+	}
+	defer file.Close()
+
+	var nread, nwrite uint64
+	var foundRead, foundWrite bool
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) < 3 {
+			continue
+		}
+		var target *uint64
+		switch fields[0] {
+		case "nread":
+			target = &nread
+			foundRead = true
+		case "nwritten":
+			target = &nwrite
+			foundWrite = true
+		default:
+			continue
+		}
+		value, err := strconv.ParseUint(fields[2], 10, 64)
+		if err != nil {
+			return 0, 0, fmt.Errorf("parsing %s in %s: %w", fields[0], path, err)
+		}
+		*target = value
+	}
+	if err := scanner.Err(); err != nil {
+		return 0, 0, err
+	}
+	if !foundRead || !foundWrite {
+		return 0, 0, fmt.Errorf("incomplete I/O counters in %s", path)
+	}
+	return nread, nwrite, nil
+}

agent/zfs/zfs_linux_test.go

@@ -0,0 +1,90 @@
+//go:build testing && linux
+
+package zfs
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPoolKernelStats(t *testing.T) {
+	root := t.TempDir()
+	oldPath := procZfsPath
+	procZfsPath = root
+	t.Cleanup(func() { procZfsPath = oldPath })
+
+	poolDir := filepath.Join(root, "tank")
+	require.NoError(t, os.MkdirAll(poolDir, 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(poolDir, "io"), []byte(
+		"11 3 0x00 1 80 0 0\n"+
+			"nread nwritten reads writes wtime wlentime wupdate rtime rlentime rupdate wcnt rcnt\n"+
+			"1884160 6450688 22 978 0 0 0 0 0 0 0 0\n",
+	), 0o644))
+	require.NoError(t, os.WriteFile(filepath.Join(poolDir, "state"), []byte("DEGRADED\n"), 0o644))
+
+	stats, err := PoolKernelStats()
+	require.NoError(t, err)
+	require.Len(t, stats, 1)
+	assert.Equal(t, PoolKernelStat{
+		Name: "tank", Health: "DEGRADED", NRead: 1884160, NWrite: 6450688,
+	}, stats[0])
+}
+
+func TestPoolKernelStatsOpenZfs24(t *testing.T) {
+	root := t.TempDir()
+	oldPath := procZfsPath
+	procZfsPath = root
+	t.Cleanup(func() { procZfsPath = oldPath })
+
+	poolDir := filepath.Join(root, "tank")
+	require.NoError(t, os.MkdirAll(poolDir, 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(poolDir, "state"), []byte("ONLINE\n"), 0o644))
+	require.NoError(t, os.WriteFile(filepath.Join(poolDir, "objset-0x1"), []byte(
+		"34 1 0x01 28 7872 0 0\n"+
+			"name type data\n"+
+			"dataset_name 7 tank\n"+
+			"nwritten 4 2000\n"+
+			"nread 4 1000\n",
+	), 0o644))
+	require.NoError(t, os.WriteFile(filepath.Join(poolDir, "objset-0x2"), []byte(
+		"34 1 0x01 28 7872 0 0\n"+
+			"name type data\n"+
+			"dataset_name 7 tank/videos\n"+
+			"nwritten 4 400\n"+
+			"nread 4 300\n",
+	), 0o644))
+
+	stats, err := PoolKernelStats()
+	require.NoError(t, err)
+	require.Len(t, stats, 1)
+	assert.Equal(t, PoolKernelStat{
+		Name: "tank", Health: "ONLINE", NRead: 1300, NWrite: 2400,
+	}, stats[0])
+}
+
+func TestPoolKernelStatsNoZfs(t *testing.T) {
+	oldPath := procZfsPath
+	procZfsPath = t.TempDir()
+	t.Cleanup(func() { procZfsPath = oldPath })
+
+	_, err := PoolKernelStats()
+	assert.ErrorIs(t, err, ErrNoZfs)
+}
+
+func TestReadPoolIORejectsMalformedCounters(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "io")
+	require.NoError(t, os.WriteFile(path, []byte("nread nwritten\nnope 10\n"), 0o644))
+	_, _, err := readPoolIO(path)
+	require.Error(t, err)
+}
+
+func TestReadObjsetIORequiresAllCounters(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "objset-0x1")
+	require.NoError(t, os.WriteFile(path, []byte("nread 4 10\n"), 0o644))
+	_, _, err := readObjsetIO(path)
+	require.Error(t, err)
+}

agent/zfs/zfs_status.go

@@ -0,0 +1,150 @@
+package zfs
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// PoolStatus holds parsed `zpool status` information for one pool.
+type PoolStatus struct {
+	Name  string
+	State string // ONLINE, DEGRADED, FAULTED, ...
+	Scrub ScrubStatus
+	Vdevs []VdevStatus
+}
+
+// ScrubStatus holds the scrub (or resilver) status parsed from the scan line.
+type ScrubStatus struct {
+	State    string // NONE, SCANNING, FINISHED, CANCELED
+	Progress string // e.g. "10.00%" while scanning
+	Errors   uint64
+}
+
+// VdevStatus is a single vdev row (mirror, raidz, or leaf disk).
+type VdevStatus struct {
+	Name         string
+	State        string
+	ReadErrs     uint64
+	WriteErrs    uint64
+	ChecksumErrs uint64
+}
+
+var (
+	progressRe = regexp.MustCompile(`(\d+\.\d+)%\s+done`)
+	errorsRe   = regexp.MustCompile(`with\s+(\d+)\s+errors`)
+)
+
+// PoolStatuses runs `zpool status` and parses per-pool state, scrub, and vdev
+// information. The human-readable format has been stable across OpenZFS
+// releases; rows are matched by their tabular shape rather than position.
+func PoolStatuses() ([]PoolStatus, error) {
+	out, err := commandOutput("zpool", "status")
+	if err != nil {
+		return nil, fmt.Errorf("zpool status: %w", err)
+	}
+	return parseZpoolStatusOutput(out)
+}
+
+// parseZpoolStatusOutput parses the output of `zpool status`.
+func parseZpoolStatusOutput(out []byte) ([]PoolStatus, error) {
+	var pools []PoolStatus
+	var current *PoolStatus
+	inConfig := false
+	scanContinuation := false // next non-blank line continues the scan line (progress)
+
+	scanner := bufio.NewScanner(bytes.NewReader(out))
+	for scanner.Scan() {
+		line := scanner.Text()
+		trimmed := strings.TrimSpace(line)
+
+		switch {
+		case strings.HasPrefix(trimmed, "pool:"):
+			pools = append(pools, PoolStatus{Name: strings.TrimSpace(strings.TrimPrefix(trimmed, "pool:"))})
+			current = &pools[len(pools)-1]
+			inConfig = false
+			scanContinuation = false
+		case current == nil:
+			continue
+		case strings.HasPrefix(trimmed, "state:"):
+			current.State = strings.TrimSpace(strings.TrimPrefix(trimmed, "state:"))
+		case strings.HasPrefix(trimmed, "scan:"):
+			current.Scrub = parseScanLine(trimmed)
+			// zpool status prints the progress percentage on the line after scan.
+			scanContinuation = true
+		case trimmed == "config:":
+			inConfig = true
+		case scanContinuation:
+			// The line after scan: may be an indented progress continuation.
+			if m := progressRe.FindStringSubmatch(trimmed); m != nil {
+				current.Scrub.Progress = m[1] + "%"
+			}
+			scanContinuation = false
+		case inConfig && (line == "" || strings.HasPrefix(line, " ") || strings.HasPrefix(line, "\t")):
+			// Table rows are indented; blank lines separate sections. The
+			// column header and the pool's own row are skipped.
+			if trimmed != "" && !strings.HasPrefix(trimmed, "NAME") {
+				if vdev, ok := parseVdevLine(trimmed, current.Name); ok {
+					current.Vdevs = append(current.Vdevs, vdev)
+				}
+			}
+		case inConfig:
+			// unindented line (errors:, status:, next pool:) ends the table
+			inConfig = false
+		}
+	}
+	return pools, scanner.Err()
+}
+
+// parseScanLine maps a `scan:` line to a ScrubStatus.
+func parseScanLine(line string) ScrubStatus {
+	var scrub ScrubStatus
+	switch {
+	case strings.Contains(line, "in progress"):
+		scrub.State = "SCANNING"
+	case strings.Contains(line, "canceled"):
+		scrub.State = "CANCELED"
+	case strings.Contains(line, "repaired"), strings.Contains(line, "resilvered"):
+		scrub.State = "FINISHED"
+	default:
+		scrub.State = "NONE"
+	}
+	if m := progressRe.FindStringSubmatch(line); m != nil {
+		scrub.Progress = m[1] + "%"
+	}
+	if m := errorsRe.FindStringSubmatch(line); m != nil {
+		if n, err := strconv.ParseUint(m[1], 10, 64); err == nil {
+			scrub.Errors = n
+		}
+	}
+	return scrub
+}
+
+// parseVdevLine parses one row of the config table. Rows have the shape
+// "NAME STATE READ WRITE CKSUM [extra...]". The first data row is the pool
+// itself and is skipped since it duplicates pool-level info.
+func parseVdevLine(line, poolName string) (VdevStatus, bool) {
+	fields := strings.Fields(line)
+	if len(fields) < 5 {
+		return VdevStatus{}, false
+	}
+	if fields[0] == poolName {
+		return VdevStatus{}, false
+	}
+	read, err1 := strconv.ParseUint(fields[2], 10, 64)
+	write, err2 := strconv.ParseUint(fields[3], 10, 64)
+	cksum, err3 := strconv.ParseUint(fields[4], 10, 64)
+	if err1 != nil || err2 != nil || err3 != nil {
+		return VdevStatus{}, false
+	}
+	return VdevStatus{
+		Name:         fields[0],
+		State:        fields[1],
+		ReadErrs:     read,
+		WriteErrs:    write,
+		ChecksumErrs: cksum,
+	}, true
+}

agent/zfs/zfs_test.go

@@ -0,0 +1,143 @@
+//go:build testing
+
+package zfs
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func fixturePath(name string) string {
+	return filepath.Join("..", "test-data", "zfs", name)
+}
+
+func TestParseZpoolListOutput(t *testing.T) {
+	data, err := os.ReadFile(fixturePath("zpool_list.txt"))
+	require.NoError(t, err)
+
+	pools, err := parseZpoolListOutput(data)
+	require.NoError(t, err)
+	require.Len(t, pools, 2)
+
+	assert.Equal(t, PoolStat{Name: "tank", Size: 23999000000000, Alloc: 12000000000000, Free: 11999000000000, Health: "ONLINE"}, pools[0])
+	assert.Equal(t, PoolStat{Name: "rpool", Size: 1200000000000, Alloc: 900000000000, Free: 300000000000, Health: "DEGRADED"}, pools[1])
+}
+
+func TestParseZpoolListOutputIgnoresEmptyLines(t *testing.T) {
+	pools, err := parseZpoolListOutput([]byte("tank\t100\t50\t50\tONLINE\n\n"))
+	require.NoError(t, err)
+	require.Len(t, pools, 1)
+	assert.Equal(t, "tank", pools[0].Name)
+}
+
+func TestParseZpoolListOutputNoPools(t *testing.T) {
+	pools, err := parseZpoolListOutput([]byte("no pools available\n"))
+	require.NoError(t, err)
+	assert.Empty(t, pools)
+}
+
+func TestParseZpoolListOutputRejectsMalformedLine(t *testing.T) {
+	_, err := parseZpoolListOutput([]byte("tank\t100\t50\n"))
+	require.Error(t, err)
+
+	_, err = parseZpoolListOutput([]byte("tank\tnotanumber\t50\t50\tONLINE\n"))
+	require.Error(t, err)
+}
+
+func TestParseZfsListOutput(t *testing.T) {
+	data, err := os.ReadFile(fixturePath("zfs_list.txt"))
+	require.NoError(t, err)
+
+	datasets, err := parseZfsListOutput(data)
+	require.NoError(t, err)
+	require.Len(t, datasets, 9)
+
+	// Mountpoint with a space must be kept intact (tab-split only).
+	assert.Equal(t, "/tank/my media", datasets[3].Mountpoint)
+	// Unmounted datasets/zvols report "-".
+	assert.Equal(t, "-", datasets[4].Mountpoint)
+	assert.Equal(t, uint64(12000000000000), datasets[0].Used)
+	assert.Equal(t, uint64(11999000000000), datasets[0].Avail)
+}
+
+func TestParseZpoolStatusOutput(t *testing.T) {
+	data, err := os.ReadFile(fixturePath("zpool_status.txt"))
+	require.NoError(t, err)
+
+	pools, err := parseZpoolStatusOutput(data)
+	require.NoError(t, err)
+	require.Len(t, pools, 2)
+
+	tank := pools[0]
+	assert.Equal(t, "tank", tank.Name)
+	assert.Equal(t, "ONLINE", tank.State)
+	assert.Equal(t, "FINISHED", tank.Scrub.State)
+	assert.Equal(t, "", tank.Scrub.Progress)
+	assert.Equal(t, uint64(0), tank.Scrub.Errors)
+	// Pool row itself is skipped; mirror + 2 disks remain.
+	require.Len(t, tank.Vdevs, 3)
+	assert.Equal(t, "mirror-0", tank.Vdevs[0].Name)
+	assert.Equal(t, "sda", tank.Vdevs[1].Name)
+	assert.Equal(t, "sdb", tank.Vdevs[2].Name)
+
+	rpool := pools[1]
+	assert.Equal(t, "rpool", rpool.Name)
+	assert.Equal(t, "DEGRADED", rpool.State)
+	assert.Equal(t, "SCANNING", rpool.Scrub.State)
+	assert.Equal(t, "10.00%", rpool.Scrub.Progress)
+	require.Len(t, rpool.Vdevs, 3)
+	assert.Equal(t, "FAULTED", rpool.Vdevs[2].State)
+	assert.Equal(t, uint64(1), rpool.Vdevs[2].ReadErrs)
+	assert.Equal(t, uint64(2), rpool.Vdevs[2].WriteErrs)
+	assert.Equal(t, uint64(3), rpool.Vdevs[2].ChecksumErrs)
+}
+
+func TestParseScanLine(t *testing.T) {
+	assert.Equal(t, "FINISHED", parseScanLine("scan: scrub repaired 0B in 00:05:12 with 0 errors on Sun Jun  1 02:00:12 2025").State)
+	assert.Equal(t, uint64(3), parseScanLine("scan: scrub repaired 10G in 01:00:00 with 3 errors on Sun Jun  1 02:00:12 2025").Errors)
+	assert.Equal(t, "SCANNING", parseScanLine("scan: scrub in progress since Sun Jun  8 01:00:00 2025").State)
+	assert.Equal(t, "CANCELED", parseScanLine("scan: scrub canceled on Sun Jun  1 02:00:12 2025").State)
+	assert.Equal(t, "FINISHED", parseScanLine("scan: resilvered 1.23G in 00:01:00 with 0 errors on Sun Jun  1 02:00:12 2025").State)
+	assert.Equal(t, "NONE", parseScanLine("scan: none requested").State)
+}
+
+func TestCommandOutputForcesLocaleAndTimesOut(t *testing.T) {
+	t.Setenv("BESZEL_ZFS_COMMAND_HELPER", "1")
+	out, err := commandOutput(os.Args[0], "-test.run=TestZfsCommandHelperProcess", "--", "locale")
+	require.NoError(t, err)
+	assert.Equal(t, "C/C", string(out))
+
+	oldTimeout := commandTimeout
+	commandTimeout = 20 * time.Millisecond
+	t.Cleanup(func() { commandTimeout = oldTimeout })
+	_, err = commandOutput(os.Args[0], "-test.run=TestZfsCommandHelperProcess", "--", "sleep")
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "timed out")
+}
+
+func TestZfsCommandHelperProcess(t *testing.T) {
+	if os.Getenv("BESZEL_ZFS_COMMAND_HELPER") != "1" {
+		return
+	}
+	mode := ""
+	for i, arg := range os.Args {
+		if arg == "--" && i+1 < len(os.Args) {
+			mode = os.Args[i+1]
+			break
+		}
+	}
+	switch strings.TrimSpace(mode) {
+	case "locale":
+		_, _ = fmt.Printf("%s/%s", os.Getenv("LC_ALL"), os.Getenv("LANG"))
+	case "sleep":
+		time.Sleep(time.Second)
+	}
+	os.Exit(0)
+}

agent/zfs/zfs_unsupported.go

@@ -7,3 +7,7 @@ import "errors"
 func ARCSize() (uint64, error) {
 	return 0, errors.ErrUnsupported
 }
+
+func PoolKernelStats() ([]PoolKernelStat, error) {
+	return nil, errors.ErrUnsupported
+}

agent/zfs_pool.go

@@ -0,0 +1,320 @@
+package agent
+
+import (
+	"log/slog"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/henrygd/beszel/agent/zfs"
+	"github.com/henrygd/beszel/internal/entities/system"
+	zfsentity "github.com/henrygd/beszel/internal/entities/zfs"
+)
+
+// zfsDatasetUsage holds usage values for a ZFS dataset mountpoint.
+type zfsDatasetUsage struct {
+	used  uint64
+	avail uint64
+}
+
+// datasetUsageRefreshInterval controls how often `zfs list` is re-run for the
+// mountpoint usage map. Dataset inventory changes rarely.
+const datasetUsageRefreshInterval = 5 * time.Minute
+
+// poolStatsRefreshInterval controls how often `zpool list` is re-run for pool
+// capacity. Health and I/O are read from procfs on Linux, so the utility only
+// needs to refresh slow-moving space accounting.
+const poolStatsRefreshInterval = time.Minute
+
+type poolKernelSample struct {
+	nread  uint64
+	nwrite uint64
+	at     time.Time
+}
+
+// ZfsManager collects ZFS pool and dataset statistics. Collection functions
+// are fields so unit tests can substitute them (same pattern as
+// diskDiscovery.usageFn). It is safe for concurrent use by a single goroutine
+// only; callers must hold the agent lock like updateDiskUsage does.
+type ZfsManager struct {
+	poolStatsFn    func() ([]zfs.PoolStat, error)       // capacity/health source
+	datasetsFn     func() ([]zfs.Dataset, error)        // dataset inventory source
+	kernelStatsFn  func() ([]zfs.PoolKernelStat, error) // procfs pool state/I/O source
+	poolStatusesFn func() ([]zfs.PoolStatus, error)     // scrub/vdev detail source
+
+	poolData      []zfs.PoolStat // cached pool inventory (TTL below)
+	lastPoolStats time.Time
+	kernelSamples map[string]poolKernelSample
+
+	datasetUsage     map[string]zfsDatasetUsage // mountpoint -> usage
+	lastUsageRefresh time.Time
+
+	// Detail data (pools, vdevs, scrub, datasets) is cached and refreshed on
+	// an interval. Accessed from handler goroutines, so it is mutex-protected.
+	detailMu          sync.Mutex
+	detail            *zfsentity.ZfsData
+	lastDetailRefresh time.Time
+	detailInterval    time.Duration
+}
+
+// newZfsManager creates a ZfsManager wired to the system's ZFS utilities.
+func newZfsManager() *ZfsManager {
+	return &ZfsManager{
+		poolStatsFn:    zfs.PoolStats,
+		datasetsFn:     zfs.Datasets,
+		kernelStatsFn:  zfs.PoolKernelStats,
+		poolStatusesFn: zfs.PoolStatuses,
+		detailInterval: time.Hour,
+	}
+}
+
+// Update refreshes systemStats.ZfsPools with the latest pool data. I/O
+// throughput and health come from inexpensive kernel kstats on Linux. Pool
+// capacity and dataset usage come from separately cached utility calls. It is
+// a no-op when ZFS is absent.
+func (zm *ZfsManager) Update(systemStats *system.Stats) {
+	pools := zm.poolStats()
+	if len(pools) == 0 {
+		return
+	}
+
+	kernelStats, ioRates := zm.kernelStats()
+
+	if systemStats.ZfsPools == nil {
+		systemStats.ZfsPools = make(map[string]*system.ZfsPool, len(pools))
+	}
+	for i := range pools {
+		pool := &pools[i]
+		// Full precision, matching the dataset values below; the frontend
+		// formats any magnitude.
+		stats := &system.ZfsPool{
+			Total:  float64(pool.Size) / (1024 * 1024 * 1024),
+			Used:   float64(pool.Alloc) / (1024 * 1024 * 1024),
+			Health: pool.Health,
+		}
+		if kernel, exists := kernelStats[pool.Name]; exists && kernel.Health != "" {
+			stats.Health = kernel.Health
+		}
+		if io, exists := ioRates[pool.Name]; exists {
+			stats.ReadBytes = io.NRead
+			stats.WriteBytes = io.NWrite
+		}
+		slog.Debug("ZFS pool sample", "pool", pool.Name, "health", stats.Health, "used_gb", stats.Used, "read_bps", stats.ReadBytes, "write_bps", stats.WriteBytes)
+		systemStats.ZfsPools[pool.Name] = stats
+	}
+
+}
+
+// poolStats returns the cached pool inventory, re-running `zpool list` at most
+// every poolStatsRefreshInterval. On failure the previous inventory is
+// retained and the refresh is retried on the next cadence.
+func (zm *ZfsManager) poolStats() []zfs.PoolStat {
+	if zm.lastPoolStats.IsZero() || time.Since(zm.lastPoolStats) >= poolStatsRefreshInterval {
+		pools, err := zm.poolStatsFn()
+		if err != nil {
+			slog.Debug("ZFS pool stats unavailable", "err", err)
+		} else {
+			zm.poolData = pools
+		}
+		zm.lastPoolStats = time.Now()
+	}
+	return zm.poolData
+}
+
+// kernelStats reads cumulative pool counters and converts them to per-second
+// rates. Counter decreases indicate a pool export/import and reset the
+// baseline instead of producing an underflow spike.
+func (zm *ZfsManager) kernelStats() (map[string]zfs.PoolKernelStat, map[string]zfs.PoolIoStats) {
+	if zm.kernelStatsFn == nil {
+		return nil, nil
+	}
+	stats, err := zm.kernelStatsFn()
+	if err != nil {
+		slog.Debug("ZFS kernel stats unavailable", "err", err)
+		return nil, nil
+	}
+	now := time.Now()
+	byName := make(map[string]zfs.PoolKernelStat, len(stats))
+	rates := make(map[string]zfs.PoolIoStats, len(stats))
+	nextSamples := make(map[string]poolKernelSample, len(stats))
+	for _, stat := range stats {
+		byName[stat.Name] = stat
+		if previous, ok := zm.kernelSamples[stat.Name]; ok && now.After(previous.at) &&
+			stat.NRead >= previous.nread && stat.NWrite >= previous.nwrite {
+			seconds := now.Sub(previous.at).Seconds()
+			rates[stat.Name] = zfs.PoolIoStats{
+				NRead:  uint64(float64(stat.NRead-previous.nread) / seconds),
+				NWrite: uint64(float64(stat.NWrite-previous.nwrite) / seconds),
+			}
+		}
+		nextSamples[stat.Name] = poolKernelSample{nread: stat.NRead, nwrite: stat.NWrite, at: now}
+	}
+	zm.kernelSamples = nextSamples
+	return byName, rates
+}
+
+// refreshDatasetUsage re-runs `zfs list` when the refresh window has elapsed
+// and rebuilds the mountpoint-keyed usage map.
+func (zm *ZfsManager) refreshDatasetUsage() {
+	if !zm.lastUsageRefresh.IsZero() && time.Since(zm.lastUsageRefresh) < datasetUsageRefreshInterval {
+		return
+	}
+	datasets, err := zm.datasetsFn()
+	if err != nil {
+		slog.Debug("ZFS dataset usage unavailable", "err", err)
+	} else {
+		usage := make(map[string]zfsDatasetUsage, len(datasets))
+		for _, ds := range datasets {
+			if ds.Mountpoint != "" && ds.Mountpoint != "-" {
+				usage[ds.Mountpoint] = zfsDatasetUsage{used: ds.Used, avail: ds.Avail}
+			}
+		}
+		zm.datasetUsage = usage
+	}
+	zm.lastUsageRefresh = time.Now()
+}
+
+// DatasetUsage returns ZFS dataset usage keyed by mountpoint, refreshed at
+// most every datasetUsageRefreshInterval. On failure the previous map is
+// retained and a debug log is emitted.
+func (zm *ZfsManager) DatasetUsage() map[string]zfsDatasetUsage {
+	zm.refreshDatasetUsage()
+	return zm.datasetUsage
+}
+
+// GetDetail returns ZFS detail data (pool health, scrub, vdevs, datasets).
+// Scheduled requests use the cached snapshot until stale; manual requests can
+// force collection. On failure the previous snapshot is retained.
+func (zm *ZfsManager) GetDetail(force bool) *zfsentity.ZfsData {
+	zm.detailMu.Lock()
+	defer zm.detailMu.Unlock()
+
+	if force || zm.detail == nil || time.Since(zm.lastDetailRefresh) >= zm.detailInterval {
+		if data, err := zm.collectDetail(zm.detail); err != nil {
+			slog.Debug("ZFS detail collection failed", "err", err)
+			if zm.detail == nil {
+				return &zfsentity.ZfsData{}
+			}
+			return &zfsentity.ZfsData{Pools: zm.detail.Pools}
+		} else {
+			zm.detail = data
+			zm.lastDetailRefresh = time.Now()
+		}
+	}
+	if zm.detail == nil {
+		return &zfsentity.ZfsData{}
+	}
+	return zm.detail
+}
+
+// collectDetail builds a ZfsData payload from the current system state.
+func (zm *ZfsManager) collectDetail(previous *zfsentity.ZfsData) (*zfsentity.ZfsData, error) {
+	pools, err := zm.poolStatsFn()
+	if err != nil {
+		return nil, err
+	}
+	if len(pools) == 0 {
+		return &zfsentity.ZfsData{Pools: []*zfsentity.PoolDetail{}, Complete: true}, nil
+	}
+
+	statuses, statusErr := zm.poolStatusesFn()
+	if statusErr != nil {
+		slog.Debug("ZFS pool status unavailable", "err", statusErr)
+	}
+	datasets, datasetsErr := zm.datasetsFn()
+	if datasetsErr != nil {
+		slog.Debug("ZFS datasets unavailable", "err", datasetsErr)
+	}
+
+	statusByPool := make(map[string]zfs.PoolStatus, len(statuses))
+	for _, st := range statuses {
+		statusByPool[st.Name] = st
+	}
+
+	previousByPool := make(map[string]*zfsentity.PoolDetail)
+	if previous != nil {
+		for _, pool := range previous.Pools {
+			if pool != nil {
+				previousByPool[pool.Name] = pool
+			}
+		}
+	}
+
+	data := &zfsentity.ZfsData{Pools: make([]*zfsentity.PoolDetail, 0, len(pools)), Complete: true}
+	for i := range pools {
+		p := &pools[i]
+		detail := &zfsentity.PoolDetail{
+			Name:   p.Name,
+			Health: p.Health,
+			Size:   p.Size,
+			Alloc:  p.Alloc,
+			Free:   p.Free,
+		}
+		if st, ok := statusByPool[p.Name]; statusErr == nil && ok {
+			if st.Scrub.State != "" && st.Scrub.State != "NONE" {
+				detail.Scrub = &zfsentity.Scrub{
+					State:    st.Scrub.State,
+					Progress: st.Scrub.Progress,
+					Errors:   st.Scrub.Errors,
+				}
+			}
+			for _, v := range st.Vdevs {
+				detail.Vdevs = append(detail.Vdevs, &zfsentity.Vdev{
+					Name:         v.Name,
+					State:        v.State,
+					ReadErrs:     v.ReadErrs,
+					WriteErrs:    v.WriteErrs,
+					ChecksumErrs: v.ChecksumErrs,
+				})
+			}
+		} else {
+			if cached := previousByPool[p.Name]; cached != nil {
+				detail.Scrub = cached.Scrub
+				detail.Vdevs = cached.Vdevs
+			}
+		}
+		if datasetsErr == nil {
+			foundDataset := false
+			for _, ds := range datasets {
+				if poolOfDataset(ds.Name) == p.Name {
+					foundDataset = true
+					detail.Datasets = append(detail.Datasets, &zfsentity.Dataset{
+						Name:       ds.Name,
+						Used:       ds.Used,
+						Avail:      ds.Avail,
+						Mountpoint: ds.Mountpoint,
+					})
+				}
+			}
+			if !foundDataset {
+				if cached := previousByPool[p.Name]; cached != nil {
+					detail.Datasets = cached.Datasets
+				}
+			}
+		} else if cached := previousByPool[p.Name]; cached != nil {
+			detail.Datasets = cached.Datasets
+		}
+		data.Pools = append(data.Pools, detail)
+	}
+	return data, nil
+}
+
+// poolOfDataset returns the pool name for a dataset name (everything before
+// the first '/'). Datasets without a separator belong to a pool of the same
+// name.
+func poolOfDataset(name string) string {
+	if idx := strings.IndexByte(name, '/'); idx >= 0 {
+		return name[:idx]
+	}
+	return name
+}
+
+// ZfsMountpoints returns the set of mountpoints backed by ZFS datasets.
+func (zm *ZfsManager) ZfsMountpoints() map[string]bool {
+	usage := zm.DatasetUsage()
+	mountpoints := make(map[string]bool, len(usage))
+	for mountpoint := range usage {
+		mountpoints[mountpoint] = true
+	}
+	return mountpoints
+}

agent/zfs_pool_test.go

@@ -0,0 +1,245 @@
+//go:build testing
+
+package agent
+
+import (
+	"testing"
+	"time"
+
+	"github.com/henrygd/beszel/agent/zfs"
+	"github.com/henrygd/beszel/internal/entities/system"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestUpdatePopulatesZfsPools(t *testing.T) {
+	zm := &ZfsManager{}
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) {
+		return []zfs.PoolStat{{Name: "tank", Size: 23999000000000, Alloc: 12000000000000, Free: 11999000000000, Health: "DEGRADED"}}, nil
+	}
+	zm.datasetsFn = func() ([]zfs.Dataset, error) {
+		return []zfs.Dataset{
+			{Name: "tank/apps", Used: 5000000000000, Avail: 11999000000000, Mountpoint: "/tank/apps"},
+			{Name: "tank/backup", Used: 6000000000000, Avail: 11999000000000, Mountpoint: "/tank/backup"},
+			// Small zvol (Proxmox VM EFI disk): must not round to zero.
+			{Name: "rpool/vm-100-disk-2", Used: 4194304, Avail: 0, Mountpoint: "-"},
+		}, nil
+	}
+	var kernelCalls int
+	zm.kernelStatsFn = func() ([]zfs.PoolKernelStat, error) {
+		kernelCalls++
+		return []zfs.PoolKernelStat{{
+			Name: "tank", Health: "ONLINE",
+			NRead: uint64(kernelCalls-1) * 1250, NWrite: uint64(kernelCalls-1) * 5120,
+		}}, nil
+	}
+
+	var stats system.Stats
+	// The first kernel sample establishes the cumulative-counter baseline.
+	zm.Update(&stats)
+	zm.kernelSamples["tank"] = poolKernelSample{at: time.Now().Add(-time.Second)}
+	zm.Update(&stats)
+	require.NotNil(t, stats.ZfsPools)
+	require.Contains(t, stats.ZfsPools, "tank")
+	assert.InDelta(t, 22350.8105, stats.ZfsPools["tank"].Total, 0.0001) // Size in GiB
+	assert.InDelta(t, 11175.8709, stats.ZfsPools["tank"].Used, 0.0001)  // Alloc in GiB
+	assert.Equal(t, "ONLINE", stats.ZfsPools["tank"].Health)
+	assert.InDelta(t, 1250, stats.ZfsPools["tank"].ReadBytes, 5)
+	assert.InDelta(t, 5120, stats.ZfsPools["tank"].WriteBytes, 5)
+
+}
+
+// TestUpdateKernelStatsMissing verifies pools without a kernel sample report zero
+// I/O instead of erroring.
+func TestUpdateKernelStatsMissing(t *testing.T) {
+	zm := &ZfsManager{}
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) {
+		return []zfs.PoolStat{{Name: "tank", Size: 1, Alloc: 1, Health: "ONLINE"}}, nil
+	}
+	zm.datasetsFn = func() ([]zfs.Dataset, error) { return nil, nil }
+	zm.kernelStatsFn = func() ([]zfs.PoolKernelStat, error) {
+		return nil, zfs.ErrNoZfs
+	}
+
+	var stats system.Stats
+	zm.Update(&stats)
+	require.NotNil(t, stats.ZfsPools)
+	assert.Equal(t, uint64(0), stats.ZfsPools["tank"].ReadBytes)
+	assert.Equal(t, uint64(0), stats.ZfsPools["tank"].WriteBytes)
+}
+
+func TestUpdateKernelCounterReset(t *testing.T) {
+	zm := &ZfsManager{}
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) {
+		return []zfs.PoolStat{{Name: "tank", Health: "ONLINE"}}, nil
+	}
+	zm.datasetsFn = func() ([]zfs.Dataset, error) { return nil, nil }
+	zm.kernelSamples = map[string]poolKernelSample{
+		"tank": {nread: 100, nwrite: 200, at: time.Now().Add(-time.Second)},
+	}
+	zm.kernelStatsFn = func() ([]zfs.PoolKernelStat, error) {
+		return []zfs.PoolKernelStat{{Name: "tank", Health: "ONLINE", NRead: 10, NWrite: 20}}, nil
+	}
+
+	var stats system.Stats
+	zm.Update(&stats)
+	assert.Equal(t, uint64(0), stats.ZfsPools["tank"].ReadBytes)
+	assert.Equal(t, uint64(0), stats.ZfsPools["tank"].WriteBytes)
+}
+
+func TestUpdateNoZfs(t *testing.T) {
+	zm := &ZfsManager{}
+	calls := 0
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) {
+		calls++
+		return nil, zfs.ErrNoZfs
+	}
+
+	var stats system.Stats
+	zm.Update(&stats)
+	zm.Update(&stats)
+	assert.Nil(t, stats.ZfsPools)
+	assert.Equal(t, 1, calls, "failed pool discovery should be cached until the next refresh interval")
+}
+
+func TestUpdateEmptyPools(t *testing.T) {
+	zm := &ZfsManager{}
+	calls := 0
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) {
+		calls++
+		return nil, nil
+	}
+
+	var stats system.Stats
+	zm.Update(&stats)
+	zm.Update(&stats)
+	assert.Nil(t, stats.ZfsPools)
+	assert.Equal(t, 1, calls, "an empty pool inventory should be cached until the next refresh interval")
+}
+
+func TestDatasetUsage(t *testing.T) {
+	zm := &ZfsManager{}
+	calls := 0
+	zm.datasetsFn = func() ([]zfs.Dataset, error) {
+		calls++
+		return []zfs.Dataset{
+			{Name: "tank", Used: 12000000000000, Avail: 11999000000000, Mountpoint: "/tank"},
+			{Name: "tank/apps", Used: 1000000000000, Avail: 11999000000000, Mountpoint: "/tank/apps"},
+			{Name: "rpool", Used: 900000000000, Avail: 300000000000, Mountpoint: "-"}, // zvol/unmounted: excluded
+		}, nil
+	}
+
+	usage := zm.DatasetUsage()
+	require.Len(t, usage, 2)
+	assert.Equal(t, zfsDatasetUsage{used: 12000000000000, avail: 11999000000000}, usage["/tank"])
+	assert.Equal(t, zfsDatasetUsage{used: 1000000000000, avail: 11999000000000}, usage["/tank/apps"])
+	assert.Equal(t, 1, calls)
+
+	// Second call within the refresh window must not re-run the collector.
+	zm.DatasetUsage()
+	assert.Equal(t, 1, calls)
+}
+
+func TestDatasetUsageRefreshOnErrorKeepsPrevious(t *testing.T) {
+	zm := &ZfsManager{}
+	zm.datasetsFn = func() ([]zfs.Dataset, error) {
+		return []zfs.Dataset{{Name: "tank", Used: 1, Avail: 1, Mountpoint: "/tank"}}, nil
+	}
+	assert.Len(t, zm.DatasetUsage(), 1)
+
+	// Force refresh window expiry, then a failing collector.
+	zm.lastUsageRefresh = time.Now().Add(-10 * time.Minute)
+	zm.datasetsFn = func() ([]zfs.Dataset, error) {
+		return nil, zfs.ErrNoZfs
+	}
+	usage := zm.DatasetUsage()
+	assert.Len(t, usage, 1, "previous usage should be retained on error")
+}
+
+func TestGetDetailForceRefresh(t *testing.T) {
+	zm := &ZfsManager{detailInterval: time.Hour}
+	poolCalls := 0
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) {
+		poolCalls++
+		return []zfs.PoolStat{{Name: "tank", Alloc: uint64(poolCalls)}}, nil
+	}
+	zm.poolStatusesFn = func() ([]zfs.PoolStatus, error) { return nil, nil }
+	zm.datasetsFn = func() ([]zfs.Dataset, error) { return nil, nil }
+
+	first := zm.GetDetail(false)
+	assert.True(t, first.Complete)
+	require.Len(t, first.Pools, 1)
+	assert.Equal(t, uint64(1), first.Pools[0].Alloc)
+
+	cached := zm.GetDetail(false)
+	require.Len(t, cached.Pools, 1)
+	assert.Equal(t, uint64(1), cached.Pools[0].Alloc)
+	assert.Equal(t, 1, poolCalls)
+
+	refreshed := zm.GetDetail(true)
+	assert.True(t, refreshed.Complete)
+	require.Len(t, refreshed.Pools, 1)
+	assert.Equal(t, uint64(2), refreshed.Pools[0].Alloc)
+	assert.Equal(t, 2, poolCalls)
+}
+
+func TestGetDetailSuccessfulEmptyInventoryClearsCache(t *testing.T) {
+	zm := &ZfsManager{detailInterval: time.Hour}
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) {
+		return []zfs.PoolStat{{Name: "tank"}}, nil
+	}
+	zm.poolStatusesFn = func() ([]zfs.PoolStatus, error) { return nil, nil }
+	zm.datasetsFn = func() ([]zfs.Dataset, error) { return nil, nil }
+
+	require.Len(t, zm.GetDetail(false).Pools, 1)
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) { return nil, nil }
+	empty := zm.GetDetail(true)
+	assert.True(t, empty.Complete)
+	assert.Empty(t, empty.Pools)
+}
+
+func TestGetDetailFailureReturnsIncompleteCachedInventory(t *testing.T) {
+	zm := &ZfsManager{detailInterval: time.Hour}
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) {
+		return []zfs.PoolStat{{Name: "tank"}}, nil
+	}
+	zm.poolStatusesFn = func() ([]zfs.PoolStatus, error) {
+		return []zfs.PoolStatus{{Name: "tank", Vdevs: []zfs.VdevStatus{{Name: "mirror-0"}}}}, nil
+	}
+	zm.datasetsFn = func() ([]zfs.Dataset, error) {
+		return []zfs.Dataset{{Name: "tank/data"}}, nil
+	}
+	first := zm.GetDetail(false)
+	require.True(t, first.Complete)
+	require.Len(t, first.Pools[0].Vdevs, 1)
+	require.Len(t, first.Pools[0].Datasets, 1)
+
+	zm.poolStatusesFn = func() ([]zfs.PoolStatus, error) { return nil, zfs.ErrNoZfs }
+	zm.datasetsFn = func() ([]zfs.Dataset, error) { return nil, zfs.ErrNoZfs }
+	partial := zm.GetDetail(true)
+	require.True(t, partial.Complete)
+	require.Len(t, partial.Pools[0].Vdevs, 1)
+	require.Len(t, partial.Pools[0].Datasets, 1)
+
+	zm.poolStatsFn = func() ([]zfs.PoolStat, error) { return nil, zfs.ErrNoZfs }
+	lastSuccessfulRefresh := zm.lastDetailRefresh
+	failed := zm.GetDetail(true)
+	assert.False(t, failed.Complete)
+	require.Len(t, failed.Pools, 1)
+	assert.Equal(t, "tank", failed.Pools[0].Name)
+	assert.Equal(t, lastSuccessfulRefresh, zm.lastDetailRefresh)
+}
+
+func TestZfsMountpoints(t *testing.T) {
+	zm := &ZfsManager{}
+	zm.datasetsFn = func() ([]zfs.Dataset, error) {
+		return []zfs.Dataset{
+			{Name: "tank", Mountpoint: "/tank"},
+			{Name: "rpool/ROOT/pve-1", Mountpoint: "/"},
+		}, nil
+	}
+	mountpoints := zm.ZfsMountpoints()
+	assert.Len(t, mountpoints, 2)
+	assert.True(t, mountpoints["/tank"])
+	assert.True(t, mountpoints["/"])
+}

beszel.go

@@ -6,7 +6,7 @@ import "github.com/blang/semver"
 
 const (
 	// Version is the current version of the application.
-	Version = "0.18.8"
+	Version = "0.18.9"
 	// AppName is the name of the application.
 	AppName = "beszel"
 )
@@ -16,3 +16,6 @@ var MinVersionCbor = semver.MustParse("0.12.0")
 
 // MinVersionAgentResponse is the minimum supported version for AgentResponse compatibility.
 var MinVersionAgentResponse = semver.MustParse("0.13.0")
+
+// MinVersionZfsData is the minimum agent version that supports ZFS detail requests.
+var MinVersionZfsData = semver.MustParse("0.18.9")

internal/alerts/alerts.go

@@ -57,12 +57,18 @@ type SystemAlertStats struct {
 	Battery      [2]uint8                      `json:"bat"`
 	Batteries    map[string]uint8              `json:"bats"`
 	ExtraFs      map[string]SystemAlertFsStats `json:"efs"`
+	ZfsPools     map[string]SystemAlertZfsPool `json:"z"`
 }
 
 type SystemAlertGPUData struct {
 	Usage float64 `json:"u"`
 }
 
+type SystemAlertZfsPool struct {
+	Total float64 `json:"d"`
+	Used  float64 `json:"du"`
+}
+
 type SystemAlertData struct {
 	systemRecord *core.Record
 	alertData    CachedAlertData
@@ -111,6 +117,9 @@ func (am *AlertManager) bindEvents() {
 	am.hub.OnRecordAfterUpdateSuccess("alerts").BindFunc(updateHistoryOnAlertUpdate)
 	am.hub.OnRecordAfterDeleteSuccess("alerts").BindFunc(resolveHistoryOnAlertDelete)
 	am.hub.OnRecordAfterUpdateSuccess("smart_devices").BindFunc(am.handleSmartDeviceAlert)
+	am.hub.OnRecordAfterCreateSuccess("zfs_pools").BindFunc(am.handleZfsPoolCreateAlert)
+	am.hub.OnRecordAfterUpdateSuccess("zfs_pools").BindFunc(am.handleZfsPoolAlert)
+	am.hub.OnRecordAfterDeleteSuccess("zfs_pools").BindFunc(resolveZfsPoolHistoryOnDelete)
 
 	am.hub.OnServe().BindFunc(func(e *core.ServeEvent) error {
 		// Populate all alerts into cache on startup

internal/alerts/alerts_system.go

@@ -44,6 +44,14 @@ func (am *AlertManager) HandleSystemAlerts(systemRecord *core.Record, data *syst
 					maxUsedPct = usedPct
 				}
 			}
+			for _, pool := range data.Stats.ZfsPools {
+				if pool != nil && pool.Total > 0 {
+					usedPct := pool.Used / pool.Total * 100
+					if usedPct > maxUsedPct {
+						maxUsedPct = usedPct
+					}
+				}
+			}
 			val = maxUsedPct
 		case "Temperature":
 			if data.Info.DashboardTemp < 1 {
@@ -208,6 +216,16 @@ func (am *AlertManager) HandleSystemAlerts(systemRecord *core.Record, data *syst
 						alert.mapSums[key] += float32(fs.DiskUsed / fs.DiskTotal * 100)
 					}
 				}
+				// add zfs pool usage from historical record
+				for key, pool := range stats.ZfsPools {
+					if pool.Total > 0 {
+						zfsKey := zfsDiskAlertKey(key)
+						if _, ok := alert.mapSums[zfsKey]; !ok {
+							alert.mapSums[zfsKey] = 0.0
+						}
+						alert.mapSums[zfsKey] += float32(pool.Used / pool.Total * 100)
+					}
+				}
 			case "Temperature":
 				if alert.mapSums == nil {
 					alert.mapSums = make(map[string]float32, len(stats.Temperatures))
@@ -255,7 +273,7 @@ func (am *AlertManager) HandleSystemAlerts(systemRecord *core.Record, data *syst
 				sumPct := float32(value)
 				if sumPct > maxPct {
 					maxPct = sumPct
-					alert.descriptor = fmt.Sprintf("Usage of %s", key)
+					alert.descriptor = diskAlertDescriptor(key)
 				}
 			}
 			alert.val = float64(maxPct / float32(alert.count))
@@ -301,6 +319,17 @@ func (am *AlertManager) HandleSystemAlerts(systemRecord *core.Record, data *syst
 	return nil
 }
 
+func zfsDiskAlertKey(poolName string) string {
+	return "zfs:" + poolName
+}
+
+func diskAlertDescriptor(key string) string {
+	if poolName, ok := strings.CutPrefix(key, "zfs:"); ok {
+		return fmt.Sprintf("Usage of ZFS pool %s", poolName)
+	}
+	return fmt.Sprintf("Usage of %s", key)
+}
+
 func hasRepresentativeBattery(legacy [2]uint8, batteries map[string]uint8) bool {
 	return legacy != [2]uint8{} || len(batteries) > 0
 }

internal/alerts/alerts_zfs.go

@@ -0,0 +1,142 @@
+package alerts
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/pocketbase/dbx"
+	"github.com/pocketbase/pocketbase/core"
+)
+
+// handleZfsPoolAlert sends alerts when a ZFS pool health state worsens and
+// resolves the alert history entry when the pool recovers. Like the SMART
+// hook, this is automatic and does not require user opt-in.
+func (am *AlertManager) handleZfsPoolAlert(e *core.RecordEvent) error {
+	return am.handleZfsPoolHealthAlert(e, e.Record.Original().GetString("health"))
+}
+
+func (am *AlertManager) handleZfsPoolCreateAlert(e *core.RecordEvent) error {
+	return am.handleZfsPoolHealthAlert(e, "")
+}
+
+func (am *AlertManager) handleZfsPoolHealthAlert(e *core.RecordEvent, oldHealth string) error {
+	newHealth := e.Record.GetString("health")
+	oldSeverity := zfsPoolSeverity(oldHealth)
+	newSeverity := zfsPoolSeverity(newHealth)
+
+	systemID := e.Record.GetString("system")
+	if systemID == "" {
+		return e.Next()
+	}
+
+	systemRecord, err := e.App.FindRecordById("systems", systemID)
+	if err != nil {
+		e.App.Logger().Error("Failed to find system for ZFS alert", "err", err, "systemID", systemID)
+		return e.Next()
+	}
+
+	// Pool recovered to a healthy state: resolve any open history entries.
+	if newSeverity == 1 && oldSeverity > 1 {
+		resolveAllAlertHistoryRecords(e.App, e.Record.Id)
+		return e.Next()
+	}
+
+	if !shouldSendZfsPoolAlert(oldSeverity, newSeverity) {
+		return e.Next()
+	}
+
+	systemName := systemRecord.GetString("name")
+	poolName := e.Record.GetString("name")
+
+	title := fmt.Sprintf("ZFS pool %s on %s: %s", newHealth, systemName, poolName)
+	message := fmt.Sprintf("ZFS pool %s (%s) was first observed as %s", poolName, systemName, newHealth)
+	if oldSeverity > 0 {
+		message = fmt.Sprintf("ZFS pool %s (%s) health changed from %s to %s", poolName, systemName, oldHealth, newHealth)
+	}
+
+	userIDs := systemRecord.GetStringSlice("users")
+	if len(userIDs) == 0 {
+		return e.Next()
+	}
+
+	for _, userID := range userIDs {
+		if err := am.SendAlert(AlertMessageData{
+			UserID:   userID,
+			SystemID: systemID,
+			Title:    title,
+			Message:  message,
+			Link:     am.hub.MakeLink("system", systemID),
+			LinkText: "View " + systemName,
+		}); err != nil {
+			e.App.Logger().Error("Failed to send ZFS alert", "err", err, "userID", userID)
+		}
+		_ = createZfsPoolHistoryRecord(e.App, userID, systemID, e.Record.Id, poolName)
+	}
+
+	return e.Next()
+}
+
+// resolveZfsPoolHistoryOnDelete resolves open alert history entries when a
+// pool record is deleted (manually or because the pool disappeared), so the
+// UI does not keep showing an ongoing alert for a pool that no longer exists.
+func resolveZfsPoolHistoryOnDelete(e *core.RecordEvent) error {
+	resolveAllAlertHistoryRecords(e.App, e.Record.Id)
+	return e.Next()
+}
+
+// shouldSendZfsPoolAlert reports whether a health transition warrants an alert.
+// First observations of unhealthy pools and worsening transitions are reported.
+func shouldSendZfsPoolAlert(oldSeverity, newSeverity int) bool {
+	return newSeverity > 1 && (oldSeverity == 0 || newSeverity > oldSeverity)
+}
+
+// zfsPoolSeverity ranks pool health states: healthy (1), degraded (2),
+// failed/unavailable (3), unknown (0).
+func zfsPoolSeverity(health string) int {
+	switch health {
+	case "ONLINE":
+		return 1
+	case "DEGRADED":
+		return 2
+	case "FAULTED", "OFFLINE", "UNAVAIL", "REMOVED", "SUSPENDED":
+		return 3
+	default:
+		return 0
+	}
+}
+
+// createZfsPoolHistoryRecord logs a pool health alert in the alerts history so
+// it is visible in the UI without creating an editable alert configuration.
+func createZfsPoolHistoryRecord(app core.App, userID, systemID, alertID, poolName string) error {
+	collection, err := app.FindCachedCollectionByNameOrId("alerts_history")
+	if err != nil {
+		return err
+	}
+	record := core.NewRecord(collection)
+	record.Set("user", userID)
+	record.Set("system", systemID)
+	record.Set("alert_id", alertID)
+	record.Set("name", "ZFS Pool: "+poolName)
+	return app.Save(record)
+}
+
+// resolveAllAlertHistoryRecords resolves every open history entry for an alert
+// record id (one per system user).
+func resolveAllAlertHistoryRecords(app core.App, alertID string) {
+	records, err := app.FindRecordsByFilter(
+		"alerts_history",
+		"alert_id={:alert_id} && resolved=null",
+		"", 0, 0,
+		dbx.Params{"alert_id": alertID},
+	)
+	if err != nil || len(records) == 0 {
+		return
+	}
+	now := time.Now().UTC()
+	for _, record := range records {
+		record.Set("resolved", now)
+		if err := app.Save(record); err != nil {
+			app.Logger().Error("Failed to resolve ZFS alert history", "err", err, "recordId", record.Id)
+		}
+	}
+}

internal/alerts/alerts_zfs_disk_test.go

@@ -0,0 +1,145 @@
+//go:build testing
+
+package alerts_test
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/henrygd/beszel/internal/entities/system"
+	beszelTests "github.com/henrygd/beszel/internal/tests"
+
+	"github.com/pocketbase/dbx"
+	"github.com/pocketbase/pocketbase/tools/types"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestDiskAlertZfsPoolMultiMinute verifies that ZFS pool usage participates in
+// the Disk threshold alert using historical per-minute values, mirroring the
+// extra-filesystem behavior.
+func TestDiskAlertZfsPoolMultiMinute(t *testing.T) {
+	hub, user := beszelTests.GetHubWithUser(t)
+	defer hub.Cleanup()
+
+	systems, err := beszelTests.CreateSystems(hub, 1, user.Id, "up")
+	require.NoError(t, err)
+	systemRecord := systems[0]
+
+	diskAlert, err := beszelTests.CreateRecord(hub, "alerts", map[string]any{
+		"name":   "Disk",
+		"system": systemRecord.Id,
+		"user":   user.Id,
+		"value":  80, // threshold: 80%
+		"min":    2,  // requires historical averaging
+	})
+	require.NoError(t, err)
+
+	am := hub.GetAlertManager()
+	now := time.Now().UTC()
+
+	poolHigh := map[string]*system.ZfsPool{
+		"tank": {Total: 1000, Used: 920}, // 92% - above threshold
+	}
+
+	recordTimes := []time.Duration{
+		-180 * time.Second,
+		-90 * time.Second,
+		-60 * time.Second,
+		-30 * time.Second,
+	}
+
+	for _, offset := range recordTimes {
+		stats := system.Stats{
+			DiskPct:  30, // root disk at 30% - below threshold
+			ZfsPools: poolHigh,
+		}
+		statsJSON, _ := json.Marshal(stats)
+
+		recordTime := now.Add(offset)
+		record, err := beszelTests.CreateRecord(hub, "system_stats", map[string]any{
+			"system": systemRecord.Id,
+			"type":   "1m",
+			"stats":  string(statsJSON),
+		})
+		require.NoError(t, err)
+		record.SetRaw("created", recordTime.Format(types.DefaultDateLayout))
+		err = hub.SaveNoValidate(record)
+		require.NoError(t, err)
+	}
+
+	combinedDataHigh := &system.CombinedData{
+		Stats: system.Stats{
+			DiskPct:  30,
+			ZfsPools: poolHigh,
+		},
+		Info: system.Info{
+			DiskPct: 30,
+		},
+	}
+
+	systemRecord.Set("updated", now)
+	err = hub.SaveNoValidate(systemRecord)
+	require.NoError(t, err)
+
+	err = am.HandleSystemAlerts(systemRecord, combinedDataHigh)
+	require.NoError(t, err)
+
+	time.Sleep(20 * time.Millisecond)
+
+	diskAlert, err = hub.FindFirstRecordByFilter("alerts", "id={:id}", dbx.Params{"id": diskAlert.Id})
+	require.NoError(t, err)
+	assert.True(t, diskAlert.GetBool("triggered"),
+		"Alert should be triggered when ZFS pool average (92%%) exceeds threshold (80%%)")
+
+	// --- Resolution: pool drops to 50%, alert should resolve ---
+
+	poolLow := map[string]*system.ZfsPool{
+		"tank": {Total: 1000, Used: 500}, // 50% - below threshold
+	}
+
+	newNow := now.Add(2 * time.Minute)
+	for _, offset := range recordTimes {
+		stats := system.Stats{
+			DiskPct:  30,
+			ZfsPools: poolLow,
+		}
+		statsJSON, _ := json.Marshal(stats)
+
+		recordTime := newNow.Add(offset)
+		record, err := beszelTests.CreateRecord(hub, "system_stats", map[string]any{
+			"system": systemRecord.Id,
+			"type":   "1m",
+			"stats":  string(statsJSON),
+		})
+		require.NoError(t, err)
+		record.SetRaw("created", recordTime.Format(types.DefaultDateLayout))
+		err = hub.SaveNoValidate(record)
+		require.NoError(t, err)
+	}
+
+	combinedDataLow := &system.CombinedData{
+		Stats: system.Stats{
+			DiskPct:  30,
+			ZfsPools: poolLow,
+		},
+		Info: system.Info{
+			DiskPct: 30,
+		},
+	}
+
+	systemRecord.Set("updated", newNow)
+	err = hub.SaveNoValidate(systemRecord)
+	require.NoError(t, err)
+
+	err = am.HandleSystemAlerts(systemRecord, combinedDataLow)
+	require.NoError(t, err)
+
+	time.Sleep(20 * time.Millisecond)
+
+	diskAlert, err = hub.FindFirstRecordByFilter("alerts", "id={:id}", dbx.Params{"id": diskAlert.Id})
+	require.NoError(t, err)
+	assert.False(t, diskAlert.GetBool("triggered"),
+		"Alert should be resolved when ZFS pool average (50%%) drops below threshold (80%%)")
+}

internal/alerts/alerts_zfs_key_test.go

@@ -0,0 +1,15 @@
+//go:build testing
+
+package alerts
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestZfsDiskAlertKeyIsNamespaced(t *testing.T) {
+	assert.Equal(t, "zfs:tank", zfsDiskAlertKey("tank"))
+	assert.Equal(t, "Usage of ZFS pool tank", diskAlertDescriptor(zfsDiskAlertKey("tank")))
+	assert.Equal(t, "Usage of tank", diskAlertDescriptor("tank"))
+}

internal/alerts/alerts_zfs_test.go

@@ -0,0 +1,292 @@
+//go:build testing
+
+package alerts_test
+
+import (
+	"testing"
+	"time"
+
+	beszelTests "github.com/henrygd/beszel/internal/tests"
+	"github.com/pocketbase/pocketbase/core"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestZfsPoolAlertOnlineToDegraded(t *testing.T) {
+	hub, user := beszelTests.GetHubWithUser(t)
+	defer hub.Cleanup()
+
+	system, err := beszelTests.CreateRecord(hub, "systems", map[string]any{
+		"name":  "test-system",
+		"users": []string{user.Id},
+		"host":  "127.0.0.1",
+	})
+	assert.NoError(t, err)
+
+	pool, err := beszelTests.CreateRecord(hub, "zfs_pools", map[string]any{
+		"system": system.Id,
+		"name":   "tank",
+		"health": "ONLINE",
+	})
+	assert.NoError(t, err)
+
+	// Re-fetch so PocketBase tracks original values
+	pool, err = hub.FindRecordById("zfs_pools", pool.Id)
+	assert.NoError(t, err)
+
+	pool.Set("health", "DEGRADED")
+	err = hub.Save(pool)
+	assert.NoError(t, err)
+
+	time.Sleep(50 * time.Millisecond)
+
+	assert.EqualValues(t, 1, hub.TestMailer.TotalSend(), "should have 1 email sent after pool became DEGRADED")
+	lastMessage := hub.TestMailer.LastMessage()
+	assert.Contains(t, lastMessage.Subject, "ZFS pool DEGRADED on test-system")
+	assert.Contains(t, lastMessage.Subject, "tank")
+	assert.Contains(t, lastMessage.Text, "ONLINE to DEGRADED")
+}
+
+func TestZfsPoolAlertDegradedToFaulted(t *testing.T) {
+	hub, user := beszelTests.GetHubWithUser(t)
+	defer hub.Cleanup()
+
+	system, err := beszelTests.CreateRecord(hub, "systems", map[string]any{
+		"name":  "test-system",
+		"users": []string{user.Id},
+		"host":  "127.0.0.1",
+	})
+	assert.NoError(t, err)
+
+	pool, err := beszelTests.CreateRecord(hub, "zfs_pools", map[string]any{
+		"system": system.Id,
+		"name":   "rpool",
+		"health": "DEGRADED",
+	})
+	assert.NoError(t, err)
+
+	pool, err = hub.FindRecordById("zfs_pools", pool.Id)
+	assert.NoError(t, err)
+
+	pool.Set("health", "FAULTED")
+	err = hub.Save(pool)
+	assert.NoError(t, err)
+
+	time.Sleep(50 * time.Millisecond)
+
+	assert.EqualValues(t, 2, hub.TestMailer.TotalSend(), "should alert on initial DEGRADED state and later FAULTED transition")
+	lastMessage := hub.TestMailer.LastMessage()
+	assert.Contains(t, lastMessage.Subject, "ZFS pool FAULTED on test-system")
+}
+
+func TestZfsPoolAlertNoAlertOnRecovery(t *testing.T) {
+	hub, user := beszelTests.GetHubWithUser(t)
+	defer hub.Cleanup()
+
+	system, err := beszelTests.CreateRecord(hub, "systems", map[string]any{
+		"name":  "test-system",
+		"users": []string{user.Id},
+		"host":  "127.0.0.1",
+	})
+	assert.NoError(t, err)
+
+	pool, err := beszelTests.CreateRecord(hub, "zfs_pools", map[string]any{
+		"system": system.Id,
+		"name":   "tank",
+		"health": "DEGRADED",
+	})
+	assert.NoError(t, err)
+
+	// Trigger a worsening alert first
+	pool, err = hub.FindRecordById("zfs_pools", pool.Id)
+	assert.NoError(t, err)
+	pool.Set("health", "FAULTED")
+	err = hub.Save(pool)
+	assert.NoError(t, err)
+	time.Sleep(50 * time.Millisecond)
+	assert.EqualValues(t, 2, hub.TestMailer.TotalSend(), "expected alerts for initial DEGRADED state and DEGRADED -> FAULTED")
+
+	// Recovery back to ONLINE must not send a new alert
+	pool, err = hub.FindRecordById("zfs_pools", pool.Id)
+	assert.NoError(t, err)
+	pool.Set("health", "ONLINE")
+	err = hub.Save(pool)
+	assert.NoError(t, err)
+	time.Sleep(50 * time.Millisecond)
+	assert.EqualValues(t, 2, hub.TestMailer.TotalSend(), "recovery should not send a new alert")
+
+	// And the open history entry should have been resolved
+	history, err := hub.FindRecordsByFilter("alerts_history", "alert_id={:alert_id}", "", 0, 0, map[string]any{"alert_id": pool.Id})
+	assert.NoError(t, err)
+	requireHistoryResolved(t, history)
+}
+
+func TestZfsPoolAlertUnknownHealthDoesNotResolve(t *testing.T) {
+	hub, user := beszelTests.GetHubWithUser(t)
+	defer hub.Cleanup()
+
+	system, err := beszelTests.CreateRecord(hub, "systems", map[string]any{
+		"name":  "test-system",
+		"users": []string{user.Id},
+		"host":  "127.0.0.1",
+	})
+	require.NoError(t, err)
+
+	pool, err := beszelTests.CreateRecord(hub, "zfs_pools", map[string]any{
+		"system": system.Id,
+		"name":   "tank",
+		"health": "DEGRADED",
+	})
+	require.NoError(t, err)
+	time.Sleep(50 * time.Millisecond)
+
+	pool, err = hub.FindRecordById("zfs_pools", pool.Id)
+	require.NoError(t, err)
+	pool.Set("health", "")
+	require.NoError(t, hub.Save(pool))
+	time.Sleep(50 * time.Millisecond)
+
+	history, err := hub.FindRecordsByFilter("alerts_history", "alert_id={:alert_id} && resolved=null", "", 0, 0, map[string]any{"alert_id": pool.Id})
+	require.NoError(t, err)
+	require.Len(t, history, 1, "unknown health must not resolve an active alert")
+}
+
+func TestZfsPoolAlertUnknownToFaulted(t *testing.T) {
+	hub, user := beszelTests.GetHubWithUser(t)
+	defer hub.Cleanup()
+
+	system, err := beszelTests.CreateRecord(hub, "systems", map[string]any{
+		"name":  "test-system",
+		"users": []string{user.Id},
+		"host":  "127.0.0.1",
+	})
+	assert.NoError(t, err)
+
+	pool, err := beszelTests.CreateRecord(hub, "zfs_pools", map[string]any{
+		"system": system.Id,
+		"name":   "tank",
+		"health": "",
+	})
+	assert.NoError(t, err)
+
+	pool, err = hub.FindRecordById("zfs_pools", pool.Id)
+	assert.NoError(t, err)
+
+	pool.Set("health", "FAULTED")
+	err = hub.Save(pool)
+	assert.NoError(t, err)
+
+	time.Sleep(50 * time.Millisecond)
+
+	assert.EqualValues(t, 1, hub.TestMailer.TotalSend(), "should alert when a previously unknown pool becomes FAULTED")
+}
+
+func TestZfsPoolAlertOnInitialUnhealthyState(t *testing.T) {
+	hub, user := beszelTests.GetHubWithUser(t)
+	defer hub.Cleanup()
+
+	system, err := beszelTests.CreateRecord(hub, "systems", map[string]any{
+		"name":  "test-system",
+		"users": []string{user.Id},
+		"host":  "127.0.0.1",
+	})
+	require.NoError(t, err)
+
+	pool, err := beszelTests.CreateRecord(hub, "zfs_pools", map[string]any{
+		"system": system.Id,
+		"name":   "tank",
+		"health": "DEGRADED",
+	})
+	require.NoError(t, err)
+	time.Sleep(50 * time.Millisecond)
+
+	require.EqualValues(t, 1, hub.TestMailer.TotalSend())
+	assert.Contains(t, hub.TestMailer.LastMessage().Text, "first observed as DEGRADED")
+
+	pool, err = hub.FindRecordById("zfs_pools", pool.Id)
+	require.NoError(t, err)
+	require.NoError(t, hub.Save(pool))
+	time.Sleep(50 * time.Millisecond)
+	assert.EqualValues(t, 1, hub.TestMailer.TotalSend(), "unchanged unhealthy health must not duplicate alerts")
+}
+
+func TestZfsPoolAlertWritesHistory(t *testing.T) {
+	hub, user := beszelTests.GetHubWithUser(t)
+	defer hub.Cleanup()
+
+	system, err := beszelTests.CreateRecord(hub, "systems", map[string]any{
+		"name":  "test-system",
+		"users": []string{user.Id},
+		"host":  "127.0.0.1",
+	})
+	assert.NoError(t, err)
+
+	pool, err := beszelTests.CreateRecord(hub, "zfs_pools", map[string]any{
+		"system": system.Id,
+		"name":   "tank",
+		"health": "ONLINE",
+	})
+	assert.NoError(t, err)
+
+	pool, err = hub.FindRecordById("zfs_pools", pool.Id)
+	assert.NoError(t, err)
+	pool.Set("health", "FAULTED")
+	err = hub.Save(pool)
+	assert.NoError(t, err)
+
+	time.Sleep(50 * time.Millisecond)
+
+	history, err := hub.FindRecordsByFilter("alerts_history", "alert_id={:alert_id}", "", 0, 0, map[string]any{"alert_id": pool.Id})
+	assert.NoError(t, err)
+	require.Len(t, history, 1, "expected one history entry per user")
+	assert.Equal(t, "ZFS Pool: tank", history[0].GetString("name"))
+	assert.Equal(t, system.Id, history[0].GetString("system"))
+}
+
+func TestZfsPoolAlertResolvedOnRecordDelete(t *testing.T) {
+	hub, user := beszelTests.GetHubWithUser(t)
+	defer hub.Cleanup()
+
+	system, err := beszelTests.CreateRecord(hub, "systems", map[string]any{
+		"name":  "test-system",
+		"users": []string{user.Id},
+		"host":  "127.0.0.1",
+	})
+	assert.NoError(t, err)
+
+	pool, err := beszelTests.CreateRecord(hub, "zfs_pools", map[string]any{
+		"system": system.Id,
+		"name":   "tank",
+		"health": "ONLINE",
+	})
+	assert.NoError(t, err)
+
+	// Trigger an alert so an open history entry exists.
+	pool, err = hub.FindRecordById("zfs_pools", pool.Id)
+	assert.NoError(t, err)
+	pool.Set("health", "FAULTED")
+	err = hub.Save(pool)
+	assert.NoError(t, err)
+	time.Sleep(50 * time.Millisecond)
+
+	history, err := hub.FindRecordsByFilter("alerts_history", "alert_id={:alert_id} && resolved=null", "", 0, 0, map[string]any{"alert_id": pool.Id})
+	assert.NoError(t, err)
+	require.Len(t, history, 1, "expected one open history entry")
+
+	// Deleting the pool record must resolve the open entry.
+	err = hub.Delete(pool)
+	assert.NoError(t, err)
+	time.Sleep(50 * time.Millisecond)
+
+	history, err = hub.FindRecordsByFilter("alerts_history", "alert_id={:alert_id}", "", 0, 0, map[string]any{"alert_id": pool.Id})
+	assert.NoError(t, err)
+	require.Len(t, history, 1)
+	requireHistoryResolved(t, history)
+}
+
+func requireHistoryResolved(t *testing.T, history []*core.Record) {
+	t.Helper()
+	for _, record := range history {
+		assert.False(t, record.GetDateTime("resolved").Time().IsZero(), "expected history entry to be resolved")
+	}
+}

internal/common/common-ws.go

@@ -22,6 +22,8 @@ const (
 	GetSmartData
 	// Request detailed systemd service info from agent
 	GetSystemdInfo
+	// Request ZFS detail data from agent
+	GetZfsData
 	// Add new actions here...
 )
 
@@ -64,6 +66,10 @@ type DataRequestOptions struct {
 	IncludeDetails bool   `cbor:"1,keyasint"`
 }
 
+type ZfsDataRequest struct {
+	Force bool `cbor:"0,keyasint,omitempty"`
+}
+
 type ContainerLogsRequest struct {
 	ContainerID string `cbor:"0,keyasint"`
 }

internal/dockerfile_agent_alpine

@@ -23,7 +23,7 @@ COPY --from=builder /agent /agent
 # AMD GPU name lookup (used by agent on Linux when /usr/share/libdrm/amdgpu.ids is read)
 COPY --from=builder /app/agent/test-data/amdgpu.ids /usr/share/libdrm/amdgpu.ids
 
-RUN apk add --no-cache smartmontools
+RUN apk add --no-cache smartmontools zfs
 
 # Ensure data persistence across container recreations
 VOLUME ["/var/lib/beszel-agent"]

internal/entities/system/system.go

@@ -33,8 +33,6 @@ type Stats struct {
 	MaxNetworkSent float64             `json:"nsm,omitempty" cbor:"-"`
 	MaxNetworkRecv float64             `json:"nrm,omitempty" cbor:"-"`
 	Temperatures   map[string]float64  `json:"t,omitempty" cbor:"20,keyasint,omitempty"`
-	Fans           map[string]uint16   `json:"f,omitempty" cbor:"36,keyasint,omitempty"`
-	Batteries      map[string]uint8    `json:"bats,omitempty" cbor:"37,keyasint,omitempty"`
 	ExtraFs        map[string]*FsStats `json:"efs,omitempty" cbor:"21,keyasint,omitempty"`
 	GPUData        map[string]GPUData  `json:"g,omitempty" cbor:"22,keyasint,omitempty"`
 	// LoadAvg1       float64             `json:"l1,omitempty" cbor:"23,keyasint,omitempty"`
@@ -52,7 +50,20 @@ type Stats struct {
 	CpuCoresUsage     Uint8Slice           `json:"cpus,omitempty" cbor:"34,keyasint,omitempty"` // per-core busy usage [CPU0..]
 	DiskIoStats       [6]float64           `json:"dios,omitzero" cbor:"35,keyasint,omitzero"`   // [read time %, write time %, io utilization %, r_await ms, w_await ms, weighted io %]
 	MaxDiskIoStats    [6]float64           `json:"diosm,omitzero" cbor:"-"`                     // max values for DiskIoStats
-	DiskIOTotal       [2]uint64            `json:"diot,omitzero" cbor:"38,keyasint,omitzero"`   // [total read bytes, total write bytes] cumulative device counters
+	Fans              map[string]uint16    `json:"f,omitempty" cbor:"36,keyasint,omitempty"`
+	Batteries         map[string]uint8     `json:"bats,omitempty" cbor:"37,keyasint,omitempty"`
+	ZfsPools          map[string]*ZfsPool  `json:"z,omitempty" cbor:"39,keyasint,omitempty"`  // ZFS pool metrics, keyed by pool name
+	DiskIOTotal       [2]uint64            `json:"diot,omitzero" cbor:"38,keyasint,omitzero"` // [total read bytes, total write bytes] cumulative device counters
+
+}
+
+// ZfsPool holds per-pool ZFS metrics for a single collection interval.
+type ZfsPool struct {
+	Total      float64 `json:"d" cbor:"0,keyasint"`                     // total capacity in GiB
+	Used       float64 `json:"du" cbor:"1,keyasint"`                    // allocated in GiB
+	ReadBytes  uint64  `json:"rb,omitzero" cbor:"2,keyasint,omitzero"`  // read throughput in bytes/s
+	WriteBytes uint64  `json:"wb,omitzero" cbor:"3,keyasint,omitzero"`  // write throughput in bytes/s
+	Health     string  `json:"h,omitempty" cbor:"4,keyasint,omitempty"` // ONLINE, DEGRADED, FAULTED, ...
 }
 
 // Uint8Slice wraps []uint8 to customize JSON encoding while keeping CBOR efficient.
@@ -183,6 +194,7 @@ type Details struct {
 	Podman        bool          `cbor:"8,keyasint,omitempty"`
 	MemoryTotal   uint64        `cbor:"9,keyasint"`
 	SmartInterval time.Duration `cbor:"10,keyasint,omitempty"`
+	ZfsInterval   time.Duration `cbor:"11,keyasint,omitempty"` // interval for ZFS detail refresh
 }
 
 // Final data structure to return to the hub

internal/entities/zfs/zfs.go

@@ -0,0 +1,45 @@
+// Package zfs defines the ZFS detail data exchanged between agent and hub.
+package zfs
+
+// ZfsData is the detail payload returned by the agent for the GetZfsData action.
+type ZfsData struct {
+	Pools    []*PoolDetail `json:"pools,omitempty"`
+	Complete bool          `json:"complete,omitempty"`
+}
+
+// PoolDetail holds the verbose state of a single pool: capacity, health,
+// scrub, vdev, and dataset information.
+type PoolDetail struct {
+	Name     string     `json:"name"`
+	Health   string     `json:"health,omitempty"`
+	Size     uint64     `json:"size,omitempty"`  // bytes
+	Alloc    uint64     `json:"alloc,omitempty"` // bytes
+	Free     uint64     `json:"free,omitempty"`  // bytes
+	Scrub    *Scrub     `json:"scrub,omitempty"`
+	Vdevs    []*Vdev    `json:"vdevs,omitempty"`
+	Datasets []*Dataset `json:"datasets,omitempty"`
+}
+
+// Scrub holds the scrub (or resilver) status of a pool.
+type Scrub struct {
+	State    string `json:"state,omitempty"` // NONE, SCANNING, FINISHED, CANCELED
+	Progress string `json:"progress,omitempty"`
+	Errors   uint64 `json:"errors,omitempty"`
+}
+
+// Vdev is a single vdev (mirror, raidz, or leaf disk) with error counters.
+type Vdev struct {
+	Name         string `json:"name"`
+	State        string `json:"state,omitempty"`
+	ReadErrs     uint64 `json:"readErrs,omitempty"`
+	WriteErrs    uint64 `json:"writeErrs,omitempty"`
+	ChecksumErrs uint64 `json:"checksumErrs,omitempty"`
+}
+
+// Dataset is a single ZFS dataset with usage information.
+type Dataset struct {
+	Name       string `json:"name"`
+	Used       uint64 `json:"used,omitempty"`
+	Avail      uint64 `json:"avail,omitempty"`
+	Mountpoint string `json:"mount,omitempty"`
+}

internal/hub/api.go

@@ -125,6 +125,8 @@ func (h *Hub) registerApiRoutes(se *core.ServeEvent) error {
 	apiAuth.DELETE("/user-alerts", alerts.DeleteUserAlerts)
 	// refresh SMART devices for a system
 	apiAuth.POST("/smart/refresh", h.refreshSmartData).BindFunc(excludeReadOnlyRole)
+	// refresh ZFS pool details for a system
+	apiAuth.POST("/zfs/refresh", h.refreshZfsData).BindFunc(excludeReadOnlyRole)
 	// get systemd service details
 	apiAuth.GET("/systemd/info", h.getSystemdInfo)
 	// /containers routes
@@ -389,3 +391,23 @@ func (h *Hub) refreshSmartData(e *core.RequestEvent) error {
 
 	return e.JSON(http.StatusOK, map[string]string{"status": "ok"})
 }
+
+// refreshZfsData handles POST /api/beszel/zfs/refresh requests
+// Fetches fresh ZFS detail data from the agent and updates the collection
+func (h *Hub) refreshZfsData(e *core.RequestEvent) error {
+	systemID := e.Request.URL.Query().Get("system")
+	if systemID == "" {
+		return e.BadRequestError("Invalid system parameter", nil)
+	}
+
+	system, err := h.sm.GetSystem(systemID)
+	if err != nil || !system.HasUser(e.App, e.Auth) {
+		return e.NotFoundError("", nil)
+	}
+
+	if err := system.FetchAndSaveZfsPools(true); err != nil {
+		return e.InternalServerError("", err)
+	}
+
+	return e.JSON(http.StatusOK, map[string]string{"status": "ok"})
+}

internal/hub/collections.go

@@ -91,6 +91,12 @@ func setCollectionAuthSettings(app core.App) error {
 	}); err != nil {
 		return err
 	}
+	if err := applyCollectionRules(app, []string{"zfs_pools"}, collectionRules{
+		list: &systemScopedReadRule,
+		view: &systemScopedReadRule,
+	}); err != nil {
+		return err
+	}
 
 	if err := applyCollectionRules(app, []string{"fingerprints"}, collectionRules{
 		list:   &systemScopedReadRule,

internal/hub/systems/system.go

@@ -21,6 +21,7 @@ import (
 	"github.com/henrygd/beszel/internal/entities/smart"
 	"github.com/henrygd/beszel/internal/entities/system"
 	"github.com/henrygd/beszel/internal/entities/systemd"
+	"github.com/henrygd/beszel/internal/entities/zfs"
 
 	"github.com/henrygd/beszel"
 
@@ -49,6 +50,8 @@ type System struct {
 	detailsFetched atomic.Bool                // True if static system details have been fetched and saved
 	smartFetching  atomic.Bool                // True if SMART devices are currently being fetched
 	smartInterval  time.Duration              // Interval for periodic SMART data updates
+	zfsFetching    atomic.Bool                // True if ZFS pools are currently being fetched
+	zfsInterval    time.Duration              // Interval for periodic ZFS detail data updates
 }
 
 func (sm *SystemManager) NewSystem(systemId string) *System {
@@ -154,6 +157,12 @@ func (sys *System) update() error {
 			// to prevent premature expiration leading to new fetch if interval is different.
 			sys.manager.smartFetchMap.UpdateExpiration(sys.Id, sys.smartInterval+time.Minute)
 		}
+		// update zfs interval if it's set on the agent side
+		if data.Details.ZfsInterval > 0 {
+			sys.zfsInterval = data.Details.ZfsInterval
+			sys.manager.hub.Logger().Info("ZFS interval updated from agent details", "system", sys.Id, "interval", sys.zfsInterval.String())
+			sys.manager.zfsFetchMap.UpdateExpiration(sys.Id, sys.zfsInterval+time.Minute)
+		}
 	}
 
 	// Fetch and save SMART devices when system first comes online or at intervals
@@ -170,6 +179,20 @@ func (sys *System) update() error {
 		}
 	}
 
+	// Fetch and save ZFS pool details when system first comes online or at intervals
+	if backgroundZfsFetchEnabled() && sys.detailsFetched.Load() && sys.supportsZfsData() {
+		if sys.zfsInterval <= 0 {
+			sys.zfsInterval = time.Hour
+		}
+		if sys.shouldFetchZfs() && sys.zfsFetching.CompareAndSwap(false, true) {
+			sys.manager.hub.Logger().Info("ZFS fetch", "system", sys.Id, "interval", sys.zfsInterval.String())
+			go func() {
+				defer sys.zfsFetching.Store(false)
+				_ = sys.FetchAndSaveZfsPools(false)
+			}()
+		}
+	}
+
 	return err
 }
 
@@ -241,6 +264,10 @@ func (sys *System) createRecords(data *system.CombinedData) (*core.Record, error
 			}
 		}
 
+		if err := sys.syncZfsPoolHealth(txApp, data.Stats.ZfsPools); err != nil {
+			return err
+		}
+
 		// update system record (do this last because it triggers alerts and we need above records to be inserted first)
 		systemRecord.Set("status", up)
 		systemRecord.Set("info", data.Info)
@@ -558,6 +585,15 @@ func (sys *System) FetchSmartDataFromAgent() (smart.SmartDataResponse, error) {
 	return result, err
 }
 
+// FetchZfsDataFromAgent fetches ZFS detail data from the agent.
+func (sys *System) FetchZfsDataFromAgent(force bool) (*zfs.ZfsData, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+	var result zfs.ZfsData
+	err := sys.request(ctx, common.GetZfsData, common.ZfsDataRequest{Force: force}, &result)
+	return &result, err
+}
+
 func makeStableHashId(strings ...string) string {
 	hash := fnv.New32a()
 	for _, str := range strings {
@@ -728,6 +764,7 @@ func (s *System) createSSHClient() error {
 	}
 	s.agentVersion, _ = extractAgentVersion(string(client.Conn.ServerVersion()))
 	s.manager.resetFailedSmartFetchState(s.Id)
+	s.manager.resetFailedZfsFetchState(s.Id)
 	return nil
 }
 

internal/hub/systems/system_manager.go

@@ -46,6 +46,7 @@ type SystemManager struct {
 	systems       *store.Store[string, *System]         // Thread-safe store of active systems
 	sshConfig     *ssh.ClientConfig                     // SSH client configuration for system connections
 	smartFetchMap *expirymap.ExpiryMap[smartFetchState] // Stores last SMART fetch time/result; TTL is only for cleanup
+	zfsFetchMap   *expirymap.ExpiryMap[zfsFetchState]   // Stores last ZFS fetch time/result; TTL is only for cleanup
 	ctx           context.Context                       // Cancelled when the app terminates
 	cancel        context.CancelFunc                    // Cancels ctx and all child system contexts
 }
@@ -67,6 +68,7 @@ func NewSystemManager(hub hubLike) *SystemManager {
 		systems:       store.New(map[string]*System{}),
 		hub:           hub,
 		smartFetchMap: expirymap.New[smartFetchState](time.Hour),
+		zfsFetchMap:   expirymap.New[zfsFetchState](time.Hour),
 	}
 	sm.ctx, sm.cancel = context.WithCancel(context.Background())
 	return sm
@@ -343,6 +345,15 @@ func (sm *SystemManager) resetFailedSmartFetchState(systemID string) {
 	}
 }
 
+// resetFailedZfsFetchState clears only failed ZFS cooldown entries so a fresh
+// agent reconnect retries ZFS discovery immediately after configuration changes.
+func (sm *SystemManager) resetFailedZfsFetchState(systemID string) {
+	state, ok := sm.zfsFetchMap.GetOk(systemID)
+	if ok && !state.Successful {
+		sm.zfsFetchMap.Remove(systemID)
+	}
+}
+
 // createSSHClientConfig initializes the SSH client configuration for connecting to an agent's server
 func (sm *SystemManager) createSSHClientConfig() error {
 	privateKey, err := sm.hub.GetSSHKey("")

internal/hub/systems/system_zfs.go

@@ -0,0 +1,193 @@
+package systems
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/henrygd/beszel"
+	"github.com/henrygd/beszel/internal/entities/system"
+	"github.com/henrygd/beszel/internal/entities/zfs"
+	"github.com/pocketbase/dbx"
+	"github.com/pocketbase/pocketbase/core"
+)
+
+var errIncompleteZfsData = errors.New("incomplete ZFS pool inventory")
+
+type zfsFetchState struct {
+	LastAttempt int64
+	Successful  bool
+}
+
+func (sys *System) supportsZfsData() bool {
+	return sys.agentVersion.GTE(beszel.MinVersionZfsData)
+}
+
+// FetchAndSaveZfsPools fetches ZFS detail data from the agent and saves it to
+// the database. force bypasses the agent's detail cache for manual refreshes.
+func (sys *System) FetchAndSaveZfsPools(force bool) error {
+	zfsData, err := sys.FetchZfsDataFromAgent(force)
+	if err != nil {
+		sys.recordZfsFetchResult(err, 0)
+		return err
+	}
+	if zfsData == nil || !zfsData.Complete {
+		err = errIncompleteZfsData
+		sys.recordZfsFetchResult(err, 0)
+		return err
+	}
+	err = sys.saveZfsPools(zfsData)
+	sys.recordZfsFetchResult(err, len(zfsData.Pools))
+	return err
+}
+
+// recordZfsFetchResult stores a cooldown entry for the ZFS interval and marks
+// whether the last fetch produced any pools, so failed setup can retry on reconnect.
+func (sys *System) recordZfsFetchResult(err error, poolCount int) {
+	if sys.manager == nil {
+		return
+	}
+	interval := sys.zfsFetchInterval()
+	success := err == nil && poolCount > 0
+	if sys.manager.hub != nil {
+		sys.manager.hub.Logger().Info("ZFS fetch result", "system", sys.Id, "success", success, "pools", poolCount, "interval", interval.String(), "err", err)
+	}
+	sys.manager.zfsFetchMap.Set(sys.Id, zfsFetchState{LastAttempt: time.Now().UnixMilli(), Successful: success}, interval+time.Minute)
+}
+
+// shouldFetchZfs returns true when there is no active ZFS cooldown entry for this system.
+func (sys *System) shouldFetchZfs() bool {
+	if sys.manager == nil {
+		return true
+	}
+	state, ok := sys.manager.zfsFetchMap.GetOk(sys.Id)
+	if !ok {
+		return true
+	}
+	return !time.UnixMilli(state.LastAttempt).Add(sys.zfsFetchInterval()).After(time.Now())
+}
+
+// zfsFetchInterval returns the agent-provided ZFS interval or the default when unset.
+func (sys *System) zfsFetchInterval() time.Duration {
+	if sys.zfsInterval > 0 {
+		return sys.zfsInterval
+	}
+	return time.Hour
+}
+
+// saveZfsPools saves ZFS pool detail data to the zfs_pools collection and
+// removes records for pools no longer reported by a complete agent inventory.
+func (sys *System) saveZfsPools(zfsData *zfs.ZfsData) error {
+	if zfsData == nil || !zfsData.Complete {
+		return errIncompleteZfsData
+	}
+
+	hub := sys.manager.hub
+	collection, err := hub.FindCachedCollectionByNameOrId("zfs_pools")
+	if err != nil {
+		return err
+	}
+
+	return hub.RunInTransaction(func(txApp core.App) error {
+		alive := make(map[string]bool, len(zfsData.Pools))
+		for _, pool := range zfsData.Pools {
+			if pool == nil {
+				continue
+			}
+			alive[pool.Name] = true
+			if err := sys.upsertZfsPoolRecord(txApp, collection, pool); err != nil {
+				return err
+			}
+		}
+
+		existing, err := txApp.FindRecordsByFilter(
+			collection,
+			"system={:system}",
+			"", 0, 0,
+			dbx.Params{"system": sys.Id},
+		)
+		if err != nil {
+			return err
+		}
+		for _, record := range existing {
+			if !alive[record.GetString("name")] {
+				if err := txApp.Delete(record); err != nil {
+					return err
+				}
+			}
+		}
+		return nil
+	})
+}
+
+func (sys *System) upsertZfsPoolRecord(app core.App, collection *core.Collection, pool *zfs.PoolDetail) error {
+	recordID := makeStableHashId(sys.Id, pool.Name)
+
+	record, err := app.FindRecordById(collection, recordID)
+	if err != nil {
+		if !errors.Is(err, sql.ErrNoRows) {
+			return err
+		}
+		record = core.NewRecord(collection)
+		record.Set("id", recordID)
+	}
+
+	record.Set("system", sys.Id)
+	record.Set("name", pool.Name)
+	record.Set("health", pool.Health)
+	record.Set("size", pool.Size)
+	record.Set("alloc", pool.Alloc)
+	record.Set("free", pool.Free)
+	record.Set("scrub", pool.Scrub)
+	record.Set("vdevs", pool.Vdevs)
+	record.Set("datasets", pool.Datasets)
+	record.Set("details_updated", time.Now().UTC())
+
+	return app.SaveNoValidate(record)
+}
+
+// syncZfsPoolHealth persists newly discovered pools and health transitions from
+// regular system samples. Detailed fields remain owned by the hourly refresh.
+func (sys *System) syncZfsPoolHealth(app core.App, pools map[string]*system.ZfsPool) error {
+	if len(pools) == 0 {
+		return nil
+	}
+	collection, err := app.FindCachedCollectionByNameOrId("zfs_pools")
+	if err != nil {
+		return err
+	}
+	const gib = 1024 * 1024 * 1024
+	for name, pool := range pools {
+		if pool == nil {
+			continue
+		}
+		recordID := makeStableHashId(sys.Id, name)
+		record, err := app.FindRecordById(collection, recordID)
+		if err != nil {
+			if !errors.Is(err, sql.ErrNoRows) {
+				return err
+			}
+			record = core.NewRecord(collection)
+			record.Set("id", recordID)
+			record.Set("system", sys.Id)
+			record.Set("name", name)
+			record.Set("health", pool.Health)
+			record.Set("size", uint64(pool.Total*gib))
+			record.Set("alloc", uint64(pool.Used*gib))
+			record.Set("free", uint64(max(pool.Total-pool.Used, 0)*gib))
+			if err := app.SaveNoValidate(record); err != nil {
+				return fmt.Errorf("creating ZFS pool summary %q: %w", name, err)
+			}
+			continue
+		}
+		if record.GetString("health") == pool.Health {
+			continue
+		}
+		record.Set("health", pool.Health)
+		if err := app.SaveNoValidate(record); err != nil {
+			return fmt.Errorf("updating ZFS pool health %q: %w", name, err)
+		}
+	}
+	return nil
+}

internal/hub/systems/system_zfs_test.go

@@ -0,0 +1,153 @@
+//go:build testing
+
+package systems
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/blang/semver"
+	"github.com/henrygd/beszel/internal/entities/system"
+	"github.com/henrygd/beszel/internal/entities/zfs"
+	"github.com/henrygd/beszel/internal/hub/expirymap"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSupportsZfsData(t *testing.T) {
+	sys := &System{agentVersion: semver.MustParse("0.18.8")}
+	assert.False(t, sys.supportsZfsData())
+
+	sys.agentVersion = semver.MustParse("0.18.9")
+	assert.True(t, sys.supportsZfsData())
+}
+
+func TestRecordZfsFetchResult(t *testing.T) {
+	sm := &SystemManager{zfsFetchMap: expirymap.New[zfsFetchState](time.Hour)}
+	t.Cleanup(sm.zfsFetchMap.StopCleaner)
+
+	sys := &System{
+		Id:          "system-1",
+		manager:     sm,
+		zfsInterval: time.Hour,
+	}
+
+	// Successful fetch with pools
+	sys.recordZfsFetchResult(nil, 2)
+	state, ok := sm.zfsFetchMap.GetOk(sys.Id)
+	assert.True(t, ok, "expected zfs fetch result to be stored")
+	assert.True(t, state.Successful, "expected successful fetch state to be recorded")
+
+	// Failed fetch
+	sys.recordZfsFetchResult(errors.New("failed"), 0)
+	state, ok = sm.zfsFetchMap.GetOk(sys.Id)
+	assert.True(t, ok, "expected failed zfs fetch state to be stored")
+	assert.False(t, state.Successful, "expected failed zfs fetch state to be marked unsuccessful")
+
+	// Successful fetch but no pools
+	sys.recordZfsFetchResult(nil, 0)
+	state, ok = sm.zfsFetchMap.GetOk(sys.Id)
+	assert.True(t, ok, "expected fetch with zero pools to be stored")
+	assert.False(t, state.Successful, "expected fetch with zero pools to be marked unsuccessful")
+}
+
+func TestShouldFetchZfs(t *testing.T) {
+	sm := &SystemManager{zfsFetchMap: expirymap.New[zfsFetchState](time.Hour)}
+	t.Cleanup(sm.zfsFetchMap.StopCleaner)
+
+	sys := &System{
+		Id:          "system-1",
+		manager:     sm,
+		zfsInterval: time.Hour,
+	}
+
+	assert.True(t, sys.shouldFetchZfs(), "expected initial zfs fetch to be allowed")
+
+	sys.recordZfsFetchResult(errors.New("failed"), 0)
+	assert.False(t, sys.shouldFetchZfs(), "expected zfs fetch to be blocked while interval entry exists")
+
+	sm.zfsFetchMap.Remove(sys.Id)
+	assert.True(t, sys.shouldFetchZfs(), "expected zfs fetch to be allowed after interval entry is cleared")
+}
+
+func TestZfsFetchIntervalDefault(t *testing.T) {
+	sys := &System{}
+	assert.Equal(t, time.Hour, sys.zfsFetchInterval())
+
+	sys.zfsInterval = 5 * time.Minute
+	assert.Equal(t, 5*time.Minute, sys.zfsFetchInterval())
+}
+
+func TestResetFailedZfsFetchState(t *testing.T) {
+	sm := &SystemManager{zfsFetchMap: expirymap.New[zfsFetchState](time.Hour)}
+	t.Cleanup(sm.zfsFetchMap.StopCleaner)
+
+	sm.zfsFetchMap.Set("system-1", zfsFetchState{LastAttempt: time.Now().UnixMilli(), Successful: false}, time.Hour)
+	sm.resetFailedZfsFetchState("system-1")
+	_, ok := sm.zfsFetchMap.GetOk("system-1")
+	assert.False(t, ok, "expected failed zfs fetch state to be cleared on reconnect")
+
+	sm.zfsFetchMap.Set("system-1", zfsFetchState{LastAttempt: time.Now().UnixMilli(), Successful: true}, time.Hour)
+	sm.resetFailedZfsFetchState("system-1")
+	_, ok = sm.zfsFetchMap.GetOk("system-1")
+	assert.True(t, ok, "expected successful zfs fetch state to be preserved")
+}
+
+func TestSaveZfsPoolsCompleteEmptyPrunesFinalPool(t *testing.T) {
+	sys, app := newTestSystemWithHub(t)
+	require.NoError(t, sys.saveZfsPools(&zfs.ZfsData{
+		Complete: true,
+		Pools:    []*zfs.PoolDetail{{Name: "tank", Health: "ONLINE"}},
+	}))
+	records, err := app.FindRecordsByFilter("zfs_pools", "system={:system}", "", 0, 0, map[string]any{"system": sys.Id})
+	require.NoError(t, err)
+	require.Len(t, records, 1)
+	assert.False(t, records[0].GetDateTime("details_updated").Time().IsZero())
+
+	require.NoError(t, sys.saveZfsPools(&zfs.ZfsData{Complete: true}))
+	records, err = app.FindRecordsByFilter("zfs_pools", "system={:system}", "", 0, 0, map[string]any{"system": sys.Id})
+	require.NoError(t, err)
+	assert.Empty(t, records)
+}
+
+func TestSaveZfsPoolsIncompletePreservesRecords(t *testing.T) {
+	sys, app := newTestSystemWithHub(t)
+	require.NoError(t, sys.saveZfsPools(&zfs.ZfsData{
+		Complete: true,
+		Pools:    []*zfs.PoolDetail{{Name: "tank", Health: "ONLINE"}},
+	}))
+	assert.ErrorIs(t, sys.saveZfsPools(&zfs.ZfsData{}), errIncompleteZfsData)
+	records, err := app.FindRecordsByFilter("zfs_pools", "system={:system}", "", 0, 0, map[string]any{"system": sys.Id})
+	require.NoError(t, err)
+	assert.Len(t, records, 1)
+}
+
+func TestSyncZfsPoolHealthWritesOnlyTransitions(t *testing.T) {
+	sys, app := newTestSystemWithHub(t)
+	collection, err := app.FindCachedCollectionByNameOrId("zfs_pools")
+	require.NoError(t, err)
+
+	require.NoError(t, sys.syncZfsPoolHealth(app, map[string]*system.ZfsPool{
+		"tank": {Total: 100, Used: 25, Health: "ONLINE"},
+	}))
+	record, err := app.FindRecordById(collection, makeStableHashId(sys.Id, "tank"))
+	require.NoError(t, err)
+	firstUpdated := record.GetDateTime("updated")
+	assert.Equal(t, "ONLINE", record.GetString("health"))
+	assert.EqualValues(t, 100*1024*1024*1024, record.GetInt("size"))
+
+	require.NoError(t, sys.syncZfsPoolHealth(app, map[string]*system.ZfsPool{
+		"tank": {Total: 100, Used: 30, Health: "ONLINE"},
+	}))
+	record, err = app.FindRecordById(collection, record.Id)
+	require.NoError(t, err)
+	assert.Equal(t, firstUpdated, record.GetDateTime("updated"))
+
+	require.NoError(t, sys.syncZfsPoolHealth(app, map[string]*system.ZfsPool{
+		"tank": {Total: 100, Used: 30, Health: "DEGRADED"},
+	}))
+	record, err = app.FindRecordById(collection, record.Id)
+	require.NoError(t, err)
+	assert.Equal(t, "DEGRADED", record.GetString("health"))
+}

internal/hub/systems/systems_production.go

@@ -7,3 +7,6 @@ package systems
 // The hub integration tests create/replace systems and clean up the test apps quickly.
 // Background SMART fetching can outlive teardown and crash in PocketBase internals (nil DB).
 func backgroundSmartFetchEnabled() bool { return true }
+
+// Background ZFS fetching follows the same policy as SMART fetching.
+func backgroundZfsFetchEnabled() bool { return true }

internal/hub/systems/systems_test_helpers.go

@@ -17,6 +17,9 @@ import (
 // the automatic background fetch during tests.
 func backgroundSmartFetchEnabled() bool { return false }
 
+// Background ZFS fetching follows the same policy as SMART fetching.
+func backgroundZfsFetchEnabled() bool { return false }
+
 // TESTING ONLY: GetSystemCount returns the number of systems in the store
 func (sm *SystemManager) GetSystemCount() int {
 	return sm.systems.Length()
@@ -115,6 +118,7 @@ func (sm *SystemManager) RemoveAllSystems() {
 		sm.RemoveSystem(system.Id)
 	}
 	sm.smartFetchMap.StopCleaner()
+	sm.zfsFetchMap.StopCleaner()
 }
 
 // ResetContextForTesting replaces the manager context for a new synctest bubble.

internal/migrations/zfs_pools.go

@@ -0,0 +1,184 @@
+package migrations
+
+import (
+	"github.com/pocketbase/pocketbase/core"
+	m "github.com/pocketbase/pocketbase/migrations"
+)
+
+// Creates the zfs_pools collection for per-system ZFS pool detail data
+// (pool health, capacity, scrub, vdevs, datasets). Upserts rather than
+// deletes missing collections, so it is safe on fresh and existing installs.
+func init() {
+	m.Register(func(app core.App) error {
+		// update collections
+		jsonData := `[
+	{
+		"createRule": null,
+		"deleteRule": null,
+		"fields": [
+			{
+				"autogeneratePattern": "[a-z0-9]{15}",
+				"hidden": false,
+				"id": "text3208210256",
+				"max": 15,
+				"min": 15,
+				"name": "id",
+				"pattern": "^[a-z0-9]+$",
+				"presentable": false,
+				"primaryKey": true,
+				"required": true,
+				"system": true,
+				"type": "text"
+			},
+			{
+				"cascadeDelete": true,
+				"collectionId": "2hz5ncl8tizk5nx",
+				"hidden": false,
+				"id": "relation1204987316",
+				"maxSelect": 1,
+				"minSelect": 0,
+				"name": "system",
+				"presentable": false,
+				"required": true,
+				"system": false,
+				"type": "relation"
+			},
+			{
+				"autogeneratePattern": "",
+				"hidden": false,
+				"id": "text7739291048",
+				"max": 0,
+				"min": 0,
+				"name": "name",
+				"pattern": "",
+				"presentable": false,
+				"primaryKey": false,
+				"required": false,
+				"system": false,
+				"type": "text"
+			},
+			{
+				"autogeneratePattern": "",
+				"hidden": false,
+				"id": "text5528164482",
+				"max": 0,
+				"min": 0,
+				"name": "health",
+				"pattern": "",
+				"presentable": false,
+				"primaryKey": false,
+				"required": false,
+				"system": false,
+				"type": "text"
+			},
+			{
+				"hidden": false,
+				"id": "number8862034195",
+				"max": null,
+				"min": null,
+				"name": "size",
+				"onlyInt": true,
+				"presentable": false,
+				"required": false,
+				"system": false,
+				"type": "number"
+			},
+			{
+				"hidden": false,
+				"id": "number4418907321",
+				"max": null,
+				"min": null,
+				"name": "alloc",
+				"onlyInt": true,
+				"presentable": false,
+				"required": false,
+				"system": false,
+				"type": "number"
+			},
+			{
+				"hidden": false,
+				"id": "number2904183765",
+				"max": null,
+				"min": null,
+				"name": "free",
+				"onlyInt": true,
+				"presentable": false,
+				"required": false,
+				"system": false,
+				"type": "number"
+			},
+			{
+				"hidden": false,
+				"id": "json4466109723",
+				"maxSize": 0,
+				"name": "scrub",
+				"presentable": false,
+				"required": false,
+				"system": false,
+				"type": "json"
+			},
+			{
+				"hidden": false,
+				"id": "json9012873456",
+				"maxSize": 0,
+				"name": "vdevs",
+				"presentable": false,
+				"required": false,
+				"system": false,
+				"type": "json"
+			},
+			{
+				"hidden": false,
+				"id": "json7182045639",
+				"maxSize": 0,
+				"name": "datasets",
+				"presentable": false,
+				"required": false,
+				"system": false,
+				"type": "json"
+			},
+			{
+				"hidden": false,
+				"id": "date9274163058",
+				"max": "",
+				"min": "",
+				"name": "details_updated",
+				"presentable": false,
+				"required": false,
+				"system": false,
+				"type": "date"
+			},
+			{
+				"hidden": false,
+				"id": "autodate3332085495",
+				"name": "updated",
+				"onCreate": true,
+				"onUpdate": true,
+				"presentable": false,
+				"system": false,
+				"type": "autodate"
+			}
+		],
+		"id": "pbc_8441057391",
+		"indexes": [
+			"CREATE INDEX ` + "`" + `idx_zfsPoolsSystem` + "`" + ` ON ` + "`" + `zfs_pools` + "`" + ` (` + "`" + `system` + "`" + `)"
+		],
+		"listRule": null,
+		"name": "zfs_pools",
+		"system": false,
+		"type": "base",
+		"updateRule": null,
+		"viewRule": null
+	}
+]`
+
+		err := app.ImportCollectionsByMarshaledJSON([]byte(jsonData), false)
+		if err != nil {
+			return err
+		}
+
+		return nil
+	}, func(app core.App) error {
+		return nil
+	})
+}

internal/records/records.go

@@ -127,6 +127,7 @@ func (rm *RecordManager) CreateLongerRecords() {
 								"created": shorterRecordPeriod,
 							},
 						)).
+						OrderBy("created").
 						All(&recordIds)
 
 					// continue if not enough shorter records
@@ -196,6 +197,7 @@ func AverageSystemStatsSlice(records []system.Stats) system.Stats {
 	tempCount := float64(0)
 	var fanSums map[string]uint64
 	fanCount := uint64(0)
+	zfsPoolCounts := make(map[string]uint64)
 
 	// Accumulate totals
 	for i := range records {
@@ -336,6 +338,31 @@ func AverageSystemStatsSlice(records []system.Stats) system.Stats {
 			}
 		}
 
+		// Accumulate ZFS pool stats. Counts are tracked per entry so a pool
+		// missing from some samples is not averaged as zero.
+		if stats.ZfsPools != nil {
+			if sum.ZfsPools == nil {
+				sum.ZfsPools = make(map[string]*system.ZfsPool, len(stats.ZfsPools))
+			}
+			for name, value := range stats.ZfsPools {
+				if value == nil {
+					continue
+				}
+				pool := sum.ZfsPools[name]
+				if pool == nil {
+					pool = &system.ZfsPool{}
+					sum.ZfsPools[name] = pool
+				}
+				pool.Total += value.Total
+				pool.Used += value.Used
+				pool.ReadBytes += value.ReadBytes
+				pool.WriteBytes += value.WriteBytes
+				if value.Health != "" {
+					pool.Health = value.Health
+				}
+				zfsPoolCounts[name]++
+			}
+		}
 		// Accumulate GPU data
 		if stats.GPUData != nil {
 			if sum.GPUData == nil {
@@ -446,6 +473,14 @@ func AverageSystemStatsSlice(records []system.Stats) system.Stats {
 		}
 	}
 
+	// Average ZFS pool stats.
+	for name, pool := range sum.ZfsPools {
+		entryCount := zfsPoolCounts[name]
+		pool.Total = twoDecimals(pool.Total / float64(entryCount))
+		pool.Used = twoDecimals(pool.Used / float64(entryCount))
+		pool.ReadBytes /= entryCount
+		pool.WriteBytes /= entryCount
+	}
 	// Average GPU data
 	if sum.GPUData != nil {
 		for id := range sum.GPUData {

internal/records/records_averaging_test.go

@@ -669,6 +669,33 @@ func TestAverageSystemStatsSlice_MixedOptionalFields(t *testing.T) {
 	assert.Equal(t, 20.0, result.GPUData["gpu0"].Usage)
 }
 
+func TestAverageSystemStatsSlice_Zfs(t *testing.T) {
+	input := []system.Stats{
+		{
+			ZfsPools: map[string]*system.ZfsPool{
+				"tank": {Total: 100, Used: 40, ReadBytes: 100, WriteBytes: 200, Health: "ONLINE"},
+			},
+		},
+		{},
+		{
+			ZfsPools: map[string]*system.ZfsPool{
+				"tank":   {Total: 120, Used: 60, ReadBytes: 300, WriteBytes: 400, Health: "DEGRADED"},
+				"backup": {Total: 50, Used: 10, ReadBytes: 25, WriteBytes: 50, Health: "ONLINE"},
+			},
+		},
+	}
+
+	result := records.AverageSystemStatsSlice(input)
+
+	require.Len(t, result.ZfsPools, 2)
+	assert.Equal(t, &system.ZfsPool{
+		Total: 110, Used: 50, ReadBytes: 200, WriteBytes: 300, Health: "DEGRADED",
+	}, result.ZfsPools["tank"])
+	assert.Equal(t, &system.ZfsPool{
+		Total: 50, Used: 10, ReadBytes: 25, WriteBytes: 50, Health: "ONLINE",
+	}, result.ZfsPools["backup"])
+}
+
 // Tests with 10 records matching the common real-world case (10 x 1m -> 1 x 10m).
 func TestAverageSystemStatsSlice_TenRecords(t *testing.T) {
 	input := make([]system.Stats, 10)

internal/site/src/components/routes/system.tsx

@@ -8,10 +8,11 @@ import { useSystemData } from "./system/use-system-data"
 import { CpuChart, ContainerCpuChart } from "./system/charts/cpu-charts"
 import { MemoryChart, ContainerMemoryChart, SwapChart } from "./system/charts/memory-charts"
 import { RootDiskCharts, ExtraFsCharts } from "./system/charts/disk-charts"
+import { ZfsCharts } from "./system/charts/zfs-charts"
 import { BandwidthChart, ContainerNetworkChart } from "./system/charts/network-charts"
 import { TemperatureChart, FanChart, BatteryChart } from "./system/charts/sensor-charts"
 import { GpuPowerChart, GpuDetailCharts } from "./system/charts/gpu-charts"
-import { LazyContainersTable, LazySmartTable, LazySystemdTable } from "./system/lazy-tables"
+import { LazyContainersTable, LazySmartTable, LazySystemdTable, LazyZfsTable } from "./system/lazy-tables"
 import { LoadAverageChart } from "./system/charts/load-average-chart"
 import { ContainerIcon, CpuIcon, HardDriveIcon, TerminalSquareIcon } from "lucide-react"
 import { GpuIcon } from "../ui/icons"
@@ -63,6 +64,7 @@ export default memo(function SystemDetail({ id }: { id: string }) {
 	const hasContainersTable = hasContainers && compareSemVer(chartData.agentVersion, SEMVER_0_14_0) >= 0
 	const hasSystemd = system.info.sv
 	const hasGpu = hasGpuData || hasGpuPowerData
+	const hasZfs = Object.keys(systemStats.at(-1)?.stats?.z ?? {}).length > 0
 
 	// keep tabsRef in sync for keyboard navigation
 	const tabs = ["core", "disk"]
@@ -142,6 +144,10 @@ export default memo(function SystemDetail({ id }: { id: string }) {
 
 				<ExtraFsCharts systemData={systemData} />
 
+				{hasZfs && <ZfsCharts systemData={systemData} />}
+
+				{hasZfs && <LazyZfsTable systemId={system.id} />}
+
 				{maybeHasSmartData && <LazySmartTable systemId={system.id} />}
 
 				{hasContainersTable && <LazyContainersTable systemId={system.id} />}
@@ -204,6 +210,8 @@ export default memo(function SystemDetail({ id }: { id: string }) {
 								<RootDiskCharts systemData={systemData} />
 							</div>
 							<ExtraFsCharts systemData={systemData} />
+							{hasZfs && <ZfsCharts systemData={systemData} />}
+							{hasZfs && <LazyZfsTable systemId={system.id} />}
 							{maybeHasSmartData && <LazySmartTable systemId={system.id} />}
 						</>
 					)}

internal/site/src/components/routes/system/charts/zfs-charts.tsx

@@ -0,0 +1,130 @@
+import { t } from "@lingui/core/macro"
+import AreaChartDefault from "@/components/charts/area-chart"
+import { decimalString, formatBytes, toFixedFloat } from "@/lib/utils"
+import type { SystemStatsRecord } from "@/types"
+import { ChartCard } from "../chart-card"
+import { Unit } from "@/lib/enums"
+import { useStore } from "@nanostores/react"
+import { $userSettings } from "@/lib/stores"
+import type { SystemData } from "../use-system-data"
+
+// Accessors for ZFS metrics
+const poolUsage =
+	(name: string) =>
+	({ stats }: SystemStatsRecord) =>
+		stats?.z?.[name]?.du ?? 0
+const poolRead =
+	(name: string) =>
+	({ stats }: SystemStatsRecord) =>
+		stats?.z?.[name]?.rb ?? 0
+const poolWrite =
+	(name: string) =>
+	({ stats }: SystemStatsRecord) =>
+		stats?.z?.[name]?.wb ?? 0
+
+export function ZfsPoolUsageChart({ systemData, poolName }: { systemData: SystemData; poolName: string }) {
+	const { chartData, grid, dataEmpty } = systemData
+	const latest = chartData.systemStats.at(-1)?.stats
+	const pool = latest?.z?.[poolName]
+	if (!pool) {
+		return null
+	}
+	let poolTotal = pool.d
+	// round to nearest GB
+	if (poolTotal >= 100) {
+		poolTotal = Math.round(poolTotal)
+	}
+
+	return (
+		<ChartCard
+			empty={dataEmpty}
+			grid={grid}
+			title={`${poolName} ${t`Usage`}`}
+			description={t`Usage of ZFS pool ${poolName}`}
+		>
+			<AreaChartDefault
+				chartData={chartData}
+				domain={[0, poolTotal]}
+				showTotal={true}
+				tickFormatter={(val) => {
+					const { value, unit } = formatBytes(val * 1024, false, Unit.Bytes, true)
+					return `${toFixedFloat(value, value >= 10 ? 0 : 1)} ${unit}`
+				}}
+				contentFormatter={({ value }) => {
+					const { value: convertedValue, unit } = formatBytes(value * 1024, false, Unit.Bytes, true)
+					return `${decimalString(convertedValue, convertedValue >= 100 ? 1 : 2)} ${unit}`
+				}}
+				dataPoints={[
+					{
+						label: t`Pool Usage`,
+						dataKey: poolUsage(poolName),
+						color: 4,
+						opacity: 0.4,
+					},
+				]}
+			/>
+		</ChartCard>
+	)
+}
+
+export function ZfsPoolIOChart({ systemData, poolName }: { systemData: SystemData; poolName: string }) {
+	const { chartData, grid, dataEmpty } = systemData
+	const userSettings = useStore($userSettings)
+	if (!chartData.systemStats?.length) {
+		return null
+	}
+	return (
+		<ChartCard
+			empty={dataEmpty}
+			grid={grid}
+			title={`${poolName} I/O`}
+			description={t`Throughput of ZFS pool ${poolName}`}
+		>
+			<AreaChartDefault
+				chartData={chartData}
+				showTotal={true}
+				dataPoints={[
+					{
+						label: t({ message: "Write", comment: "Disk write" }),
+						dataKey: poolWrite(poolName),
+						color: 3,
+						opacity: 0.3,
+					},
+					{
+						label: t({ message: "Read", comment: "Disk read" }),
+						dataKey: poolRead(poolName),
+						color: 1,
+						opacity: 0.3,
+					},
+				]}
+				tickFormatter={(val) => {
+					const { value, unit } = formatBytes(val, true, userSettings.unitDisk, false)
+					return `${toFixedFloat(value, value >= 10 ? 0 : 1)} ${unit}`
+				}}
+				contentFormatter={({ value }) => {
+					const { value: convertedValue, unit } = formatBytes(value, true, userSettings.unitDisk, false)
+					return `${decimalString(convertedValue, convertedValue >= 100 ? 1 : 2)} ${unit}`
+				}}
+			/>
+		</ChartCard>
+	)
+}
+
+/** ZFS section: one stacked usage card per pool plus per-pool I/O cards. */
+export function ZfsCharts({ systemData }: { systemData: SystemData }) {
+	const latest = systemData.chartData.systemStats?.at(-1)?.stats
+	const pools = latest?.z ?? {}
+	if (Object.keys(pools).length === 0) {
+		return null
+	}
+	return (
+		<div className="grid xl:grid-cols-2 gap-4">
+			{Object.keys(pools).map((poolName) => (
+				<div key={poolName} className="contents">
+					<ZfsPoolUsageChart systemData={systemData} poolName={poolName} />
+					<ZfsPoolIOChart systemData={systemData} poolName={poolName} />
+				</div>
+			))}
+		</div>
+	)
+}

internal/site/src/components/routes/system/lazy-tables.tsx

@@ -24,6 +24,17 @@ export function LazySmartTable({ systemId }: { systemId: string }) {
 	)
 }
 
+const ZfsTable = lazy(() => import("./zfs-table"))
+
+export function LazyZfsTable({ systemId }: { systemId: string }) {
+	const { isIntersecting, ref } = useIntersectionObserver({ rootMargin: "90px" })
+	return (
+		<div ref={ref} className={cn(isIntersecting && "contents")}>
+			{isIntersecting && <ZfsTable systemId={systemId} />}
+		</div>
+	)
+}
+
 const SystemdTable = lazy(() => import("../../systemd-table/systemd-table"))
 
 export function LazySystemdTable({ systemId }: { systemId: string }) {

internal/site/src/components/routes/system/zfs-table.tsx

@@ -0,0 +1,652 @@
+import { Alert, AlertDescription, AlertTitle } from "@/components/ui/alert"
+import { Badge } from "@/components/ui/badge"
+import { Button } from "@/components/ui/button"
+import { Card, CardDescription, CardHeader, CardTitle } from "@/components/ui/card"
+import { DropdownMenu, DropdownMenuContent, DropdownMenuItem, DropdownMenuTrigger } from "@/components/ui/dropdown-menu"
+import { Input } from "@/components/ui/input"
+import { Separator } from "@/components/ui/separator"
+import { Sheet, SheetContent, SheetDescription, SheetHeader, SheetTitle } from "@/components/ui/sheet"
+import { Table, TableBody, TableCell, TableHead, TableHeader, TableRow } from "@/components/ui/table"
+import { isReadOnlyUser, pb } from "@/lib/api"
+import { cn, formatBytes, formatShortDate, hourWithSeconds, toFixedFloat } from "@/lib/utils"
+import type { ZfsDataset, ZfsPoolRecord, ZfsVdev } from "@/types"
+import { t } from "@lingui/core/macro"
+import { Trans } from "@lingui/react/macro"
+import type { Column, ColumnDef } from "@tanstack/react-table"
+import {
+	flexRender,
+	getCoreRowModel,
+	getFilteredRowModel,
+	getSortedRowModel,
+	useReactTable,
+} from "@tanstack/react-table"
+import {
+	ActivityIcon,
+	BinaryIcon,
+	CheckCircleIcon,
+	CircleAlertIcon,
+	ClockIcon,
+	HardDriveDownloadIcon,
+	HardDriveIcon,
+	HardDriveUploadIcon,
+	LoaderCircleIcon,
+	MoreHorizontalIcon,
+	RefreshCwIcon,
+	RotateCwIcon,
+	XCircleIcon,
+	XIcon,
+} from "lucide-react"
+import { useCallback, useEffect, useMemo, useState } from "react"
+
+const ZFS_POOL_FIELDS = "id,system,name,health,size,alloc,free,scrub,details_updated,updated"
+
+/** Maps a zpool health string to a Badge variant. */
+function healthVariant(health: string): "success" | "warning" | "danger" | "outline" {
+	switch (health) {
+		case "ONLINE":
+			return "success"
+		case "DEGRADED":
+			return "warning"
+		case "FAULTED":
+		case "OFFLINE":
+		case "UNAVAIL":
+		case "REMOVED":
+		case "SUSPENDED":
+			return "danger"
+		default:
+			return "outline"
+	}
+}
+
+function formatCapacity(bytes: number): string {
+	if (!bytes) return "-"
+	const { value, unit } = formatBytes(bytes)
+	return `${toFixedFloat(value, value >= 10 ? 1 : 2)} ${unit}`
+}
+
+function HeaderButton<T>({ column, name, Icon }: { column: Column<T>; name: string; Icon: React.ElementType }) {
+	const isSorted = column.getIsSorted()
+	return (
+		<Button
+			className={cn(
+				"h-9 px-3 flex items-center gap-2 duration-50",
+				isSorted && "bg-accent/70 light:bg-accent text-accent-foreground/90"
+			)}
+			variant="ghost"
+			onClick={() => column.toggleSorting(column.getIsSorted() === "asc")}
+		>
+			<Icon className="size-4" />
+			{name}
+		</Button>
+	)
+}
+
+const columns: ColumnDef<ZfsPoolRecord>[] = [
+	{
+		accessorKey: "name",
+		sortingFn: (a, b) => a.original.name.localeCompare(b.original.name),
+		header: ({ column }) => <HeaderButton column={column} name={t`Pool`} Icon={HardDriveIcon} />,
+		cell: ({ getValue }) => <span className="font-medium ms-1.5">{getValue() as string}</span>,
+	},
+	{
+		accessorKey: "health",
+		sortingFn: (a, b) => a.original.health.localeCompare(b.original.health),
+		header: ({ column }) => <HeaderButton column={column} name={t`Health`} Icon={ActivityIcon} />,
+		cell: ({ getValue }) => {
+			const health = (getValue() as string) || ""
+			return <Badge variant={healthVariant(health)}>{health || t`Unknown`}</Badge>
+		},
+	},
+	{
+		id: "size",
+		accessorFn: (record) => record.size,
+		invertSorting: true,
+		header: ({ column }) => <HeaderButton column={column} name={t`Size`} Icon={BinaryIcon} />,
+		cell: ({ getValue }) => <span className="ms-1.5 tabular-nums">{formatCapacity(getValue() as number)}</span>,
+	},
+	{
+		id: "used",
+		accessorFn: (record) => record.alloc,
+		invertSorting: true,
+		header: ({ column }) => <HeaderButton column={column} name={t`Used`} Icon={HardDriveDownloadIcon} />,
+		cell: ({ getValue }) => <span className="ms-1.5 tabular-nums">{formatCapacity(getValue() as number)}</span>,
+	},
+	{
+		id: "free",
+		accessorFn: (record) => record.free,
+		invertSorting: true,
+		header: ({ column }) => <HeaderButton column={column} name={t`Free`} Icon={HardDriveUploadIcon} />,
+		cell: ({ getValue }) => <span className="ms-1.5 tabular-nums">{formatCapacity(getValue() as number)}</span>,
+	},
+	{
+		id: "scrub",
+		accessorFn: (record) => record.scrub?.state ?? "",
+		header: ({ column }) => <HeaderButton column={column} name={t`Scrub`} Icon={RotateCwIcon} />,
+		cell: ({ row }) => {
+			const scrub = row.original.scrub
+			if (!scrub?.state) return <span className="ms-1.5 text-muted-foreground">{t`None`}</span>
+			return (
+				<span className="ms-1.5 tabular-nums">
+					{scrub.state}
+					{scrub.progress ? ` (${scrub.progress})` : ""}
+				</span>
+			)
+		},
+	},
+	{
+		id: "updated",
+		invertSorting: true,
+		accessorFn: (record) => record.details_updated || record.updated,
+		header: ({ column }) => <HeaderButton column={column} name={t`Updated`} Icon={ClockIcon} />,
+		cell: ({ getValue }) => {
+			const timestamp = getValue() as string
+			if (!timestamp) return null
+			const formatter =
+				new Date(timestamp).toDateString() === new Date().toDateString() ? hourWithSeconds : formatShortDate
+			return <span className="ms-1 tabular-nums">{formatter(timestamp)}</span>
+		},
+	},
+]
+
+function VdevTable({ vdevs }: { vdevs: ZfsVdev[] }) {
+	if (!vdevs?.length) return null
+	return (
+		<div className="overflow-x-auto rounded-md border">
+			<Table>
+				<TableHeader>
+					<TableRow>
+						<TableHead>{t`Vdev`}</TableHead>
+						<TableHead>{t`State`}</TableHead>
+						<TableHead className="text-right">{t`Read errors`}</TableHead>
+						<TableHead className="text-right">{t`Write errors`}</TableHead>
+						<TableHead className="text-right">{t`Checksum errors`}</TableHead>
+					</TableRow>
+				</TableHeader>
+				<TableBody>
+					{vdevs.map((vdev) => (
+						<TableRow key={vdev.name}>
+							<TableCell className="font-mono text-xs">{vdev.name}</TableCell>
+							<TableCell>
+								<Badge variant={healthVariant(vdev.state ?? "")} className="font-normal">
+									{vdev.state ?? "-"}
+								</Badge>
+							</TableCell>
+							<TableCell
+								className={cn("text-right tabular-nums", (vdev.readErrs ?? 0) > 0 && "text-red-600 dark:text-red-400")}
+							>
+								{vdev.readErrs ?? 0}
+							</TableCell>
+							<TableCell
+								className={cn("text-right tabular-nums", (vdev.writeErrs ?? 0) > 0 && "text-red-600 dark:text-red-400")}
+							>
+								{vdev.writeErrs ?? 0}
+							</TableCell>
+							<TableCell
+								className={cn(
+									"text-right tabular-nums",
+									(vdev.checksumErrs ?? 0) > 0 && "text-red-600 dark:text-red-400"
+								)}
+							>
+								{vdev.checksumErrs ?? 0}
+							</TableCell>
+						</TableRow>
+					))}
+				</TableBody>
+			</Table>
+		</div>
+	)
+}
+
+const datasetColumns: ColumnDef<ZfsDataset>[] = [
+	{
+		accessorKey: "name",
+		sortingFn: (a, b) => a.original.name.localeCompare(b.original.name),
+		header: ({ column }) => <HeaderButton column={column} name={t`Dataset`} Icon={HardDriveIcon} />,
+		cell: ({ getValue }) => <span className="font-mono text-xs">{getValue() as string}</span>,
+	},
+	{
+		id: "used",
+		accessorFn: (ds) => ds.used ?? 0,
+		invertSorting: true,
+		header: ({ column }) => <HeaderButton column={column} name={t`Used`} Icon={HardDriveDownloadIcon} />,
+		cell: ({ getValue }) => <span className="text-right tabular-nums">{formatCapacity(getValue() as number)}</span>,
+	},
+	{
+		id: "avail",
+		accessorFn: (ds) => ds.avail ?? 0,
+		invertSorting: true,
+		header: ({ column }) => <HeaderButton column={column} name={t`Available`} Icon={HardDriveUploadIcon} />,
+		cell: ({ getValue }) => <span className="text-right tabular-nums">{formatCapacity(getValue() as number)}</span>,
+	},
+	{
+		accessorKey: "mount",
+		sortingFn: (a, b) => (a.original.mount ?? "").localeCompare(b.original.mount ?? ""),
+		header: ({ column }) => <HeaderButton column={column} name={t`Mountpoint`} Icon={HardDriveIcon} />,
+		cell: ({ getValue }) => (
+			<span className="font-mono text-xs text-muted-foreground">{(getValue() as string) || "-"}</span>
+		),
+	},
+]
+
+function DatasetTable({ datasets }: { datasets: ZfsDataset[] }) {
+	const [filter, setFilter] = useState("")
+	const filtered = useMemo(() => {
+		if (!datasets) return []
+		if (!filter) return datasets
+		const needle = filter.toLowerCase()
+		return datasets.filter((ds) => ds.name.toLowerCase().includes(needle))
+	}, [datasets, filter])
+
+	const table = useReactTable({
+		data: filtered,
+		columns: datasetColumns,
+		getCoreRowModel: getCoreRowModel(),
+		getSortedRowModel: getSortedRowModel(),
+	})
+
+	if (!datasets?.length) return null
+	return (
+		<div>
+			<div className="mb-2 flex items-center justify-between gap-4">
+				<h3 className="text-base font-semibold">
+					<Trans>Datasets</Trans>
+				</h3>
+				<div className="relative w-64 max-w-full">
+					<Input
+						placeholder={t`Filter datasets...`}
+						value={filter}
+						onChange={(e) => setFilter(e.target.value)}
+						className="px-4 w-full"
+					/>
+					{filter && (
+						<Button
+							type="button"
+							variant="ghost"
+							size="icon"
+							aria-label={t`Clear`}
+							className="absolute right-1 top-1/2 -translate-y-1/2 h-7 w-7 text-muted-foreground"
+							onClick={() => setFilter("")}
+						>
+							<XIcon className="h-4 w-4" />
+						</Button>
+					)}
+				</div>
+			</div>
+			<div className="max-h-80 overflow-auto rounded-md border">
+				<Table>
+					<TableHeader className="sticky top-0 z-10">
+						{table.getHeaderGroups().map((headerGroup) => (
+							<TableRow key={headerGroup.id}>
+								{headerGroup.headers.map((header) => (
+									<TableHead key={header.id} className="px-2">
+										{header.isPlaceholder ? null : flexRender(header.column.columnDef.header, header.getContext())}
+									</TableHead>
+								))}
+							</TableRow>
+						))}
+					</TableHeader>
+					<TableBody>
+						{table.getRowModel().rows.map((row) => (
+							<TableRow key={row.id}>
+								{row.getVisibleCells().map((cell) => (
+									<TableCell key={cell.id} className="ps-5 whitespace-pre">
+										{flexRender(cell.column.columnDef.cell, cell.getContext())}
+									</TableCell>
+								))}
+							</TableRow>
+						))}
+					</TableBody>
+				</Table>
+			</div>
+		</div>
+	)
+}
+
+function PoolSheet({
+	poolId,
+	open,
+	onOpenChange,
+}: {
+	poolId: string | null
+	open: boolean
+	onOpenChange: (open: boolean) => void
+}) {
+	const [pool, setPool] = useState<ZfsPoolRecord | null>(null)
+	const [isLoading, setIsLoading] = useState(false)
+
+	useEffect(() => {
+		let active = true
+		if (!poolId) {
+			setPool(null)
+			return
+		}
+		// Only fetch when opening, not when closing (keeps data visible during close animation)
+		if (!open) return
+		setIsLoading(true)
+		pb.collection("zfs_pools")
+			.getOne(poolId)
+			.then((record) => active && setPool(record as ZfsPoolRecord))
+			.catch(() => active && setPool(null))
+			.finally(() => active && setIsLoading(false))
+		return () => {
+			active = false
+		}
+	}, [open, poolId])
+
+	const health = pool?.health || ""
+	const healthVariantValue = healthVariant(health)
+	const HealthIcon =
+		healthVariantValue === "success"
+			? CheckCircleIcon
+			: healthVariantValue === "warning"
+				? CircleAlertIcon
+				: XCircleIcon
+
+	return (
+		<Sheet open={open} onOpenChange={onOpenChange}>
+			<SheetContent className="w-full sm:max-w-220 gap-0 overflow-y-auto">
+				<SheetHeader className="mb-0 border-b">
+					<SheetTitle className="flex items-center gap-2">
+						{pool ? pool.name : t`ZFS Pool`}
+						{pool && <Badge variant={healthVariantValue}>{health}</Badge>}
+					</SheetTitle>
+					<SheetDescription className="flex flex-wrap items-center gap-x-2 gap-y-1">
+						{pool?.size ? formatCapacity(pool.size) : null}
+						{pool?.alloc ? (
+							<>
+								<Separator orientation="vertical" className="h-2.5 bg-muted-foreground opacity-70" />
+								<span>
+									<Trans>Used</Trans>: {formatCapacity(pool.alloc)}
+								</span>
+							</>
+						) : null}
+						{pool?.free ? (
+							<>
+								<Separator orientation="vertical" className="h-2.5 bg-muted-foreground opacity-70" />
+								<span>
+									<Trans>Free</Trans>: {formatCapacity(pool.free)}
+								</span>
+							</>
+						) : null}
+					</SheetDescription>
+				</SheetHeader>
+				<div className="flex-1 p-4 flex flex-col gap-4">
+					{isLoading ? (
+						<div className="flex justify-center py-8">
+							<LoaderCircleIcon className="animate-spin size-10 opacity-60" />
+						</div>
+					) : (
+						<>
+							{pool && health && (
+								<Alert className="pb-3 shrink-0">
+									<HealthIcon className="size-4" />
+									<AlertTitle>
+										<Trans>Pool Health</Trans>: {health}
+									</AlertTitle>
+									{pool.scrub?.state && (
+										<AlertDescription>
+											<Trans>Scrub</Trans>: {pool.scrub.state}
+											{pool.scrub.progress ? ` (${pool.scrub.progress})` : ""}
+											{pool.scrub.errors ? `, ${pool.scrub.errors} errors` : ""}
+										</AlertDescription>
+									)}
+								</Alert>
+							)}
+							{pool?.vdevs?.length || pool?.datasets?.length ? (
+								<>
+									{pool.vdevs?.length ? <VdevTable vdevs={pool.vdevs} /> : null}
+									<DatasetTable datasets={pool.datasets ?? []} />
+								</>
+							) : (
+								!isLoading && (
+									<div className="py-8 text-center text-sm text-muted-foreground">
+										<Trans>No detail data for this pool.</Trans>
+									</div>
+								)
+							)}
+						</>
+					)}
+				</div>
+			</SheetContent>
+		</Sheet>
+	)
+}
+
+export default function ZfsTable({ systemId }: { systemId?: string }) {
+	const [zfsPools, setZfsPools] = useState<ZfsPoolRecord[]>()
+	const [globalFilter, setGlobalFilter] = useState("")
+	const [activePoolId, setActivePoolId] = useState<string | null>(null)
+	const [sheetOpen, setSheetOpen] = useState(false)
+	const [refreshingId, setRefreshingId] = useState<string | null>(null)
+
+	useEffect(() => {
+		let disposed = false
+		let unsubscribe: () => void = () => {}
+		// fetch initial records
+		pb.collection<ZfsPoolRecord>("zfs_pools")
+			.getFullList({
+				filter: systemId ? pb.filter("system={:id}", { id: systemId }) : "",
+				sort: "name",
+				fields: ZFS_POOL_FIELDS,
+			})
+			.then((records) => !disposed && setZfsPools(records))
+			.catch((error) => console.error("Failed to fetch ZFS pools:", error))
+
+		// subscribe to realtime updates
+		const pbOptions = systemId ? { filter: `system="${systemId}"` } : undefined
+		;(async () => {
+			try {
+				const unsubscribeNow = await pb.collection<ZfsPoolRecord>("zfs_pools").subscribe(
+					"*",
+					(event) => {
+						const record = event.record as ZfsPoolRecord
+						setZfsPools((current) => {
+							const pools = current ?? []
+							const matchesSystemScope = !systemId || record.system === systemId
+							if (event.action === "delete") {
+								return pools.filter((pool) => pool.id !== record.id)
+							}
+							if (!matchesSystemScope) {
+								return pools.filter((pool) => pool.id !== record.id)
+							}
+							const existingIndex = pools.findIndex((pool) => pool.id === record.id)
+							if (existingIndex === -1) {
+								return [record, ...pools]
+							}
+							const next = [...pools]
+							next[existingIndex] = record
+							return next
+						})
+					},
+					pbOptions
+				)
+				if (disposed) {
+					unsubscribeNow()
+				} else {
+					unsubscribe = unsubscribeNow
+				}
+			} catch (error) {
+				console.error("Failed to subscribe to ZFS pool updates:", error)
+			}
+		})()
+
+		return () => {
+			disposed = true
+			unsubscribe?.()
+		}
+	}, [systemId])
+
+	const refreshSystem = useCallback(async (systemId: string) => {
+		try {
+			await pb.send("/api/beszel/zfs/refresh", {
+				method: "POST",
+				query: { system: systemId },
+			})
+		} catch (error) {
+			console.error("Failed to refresh ZFS pools:", error)
+		}
+	}, [])
+
+	const handleRowRefresh = useCallback(
+		async (pool: ZfsPoolRecord) => {
+			if (!pool.system) return
+			setRefreshingId(pool.id)
+			try {
+				await refreshSystem(pool.system)
+			} finally {
+				setRefreshingId((id) => (id === pool.id ? null : id))
+			}
+		},
+		[refreshSystem]
+	)
+
+	const actionColumn = useMemo<ColumnDef<ZfsPoolRecord>>(
+		() => ({
+			id: "actions",
+			enableSorting: false,
+			header: () => (
+				<span className="sr-only">
+					<Trans>Actions</Trans>
+				</span>
+			),
+			cell: ({ row }) => {
+				const pool = row.original
+				const isRowRefreshing = refreshingId === pool.id
+
+				return (
+					<div className="flex justify-end">
+						<DropdownMenu>
+							<DropdownMenuTrigger asChild>
+								<Button
+									variant="ghost"
+									size="icon"
+									className="size-10"
+									onClick={(event) => event.stopPropagation()}
+									onMouseDown={(event) => event.stopPropagation()}
+								>
+									<span className="sr-only">
+										<Trans>Open menu</Trans>
+									</span>
+									<MoreHorizontalIcon className="w-5" />
+								</Button>
+							</DropdownMenuTrigger>
+							<DropdownMenuContent align="end" onClick={(event) => event.stopPropagation()}>
+								<DropdownMenuItem
+									onClick={(event) => {
+										event.stopPropagation()
+										handleRowRefresh(pool)
+									}}
+									disabled={isRowRefreshing}
+								>
+									<RefreshCwIcon className={cn("me-2.5 size-4", isRowRefreshing && "animate-spin")} />
+									<Trans>Refresh</Trans>
+								</DropdownMenuItem>
+							</DropdownMenuContent>
+						</DropdownMenu>
+					</div>
+				)
+			},
+		}),
+		[refreshingId, handleRowRefresh]
+	)
+
+	const tableColumns = useMemo(() => {
+		return isReadOnlyUser() ? columns : [...columns, actionColumn]
+	}, [actionColumn])
+
+	const table = useReactTable({
+		data: zfsPools || ([] as ZfsPoolRecord[]),
+		columns: tableColumns,
+		getCoreRowModel: getCoreRowModel(),
+		getSortedRowModel: getSortedRowModel(),
+		getFilteredRowModel: getFilteredRowModel(),
+		state: { globalFilter },
+		onGlobalFilterChange: setGlobalFilter,
+		globalFilterFn: (row, _columnId, filterValue) => {
+			const pool = row.original
+			const searchString = `${pool.name} ${pool.health ?? ""}`.toLowerCase()
+			return (filterValue as string)
+				.toLowerCase()
+				.split(" ")
+				.every((term) => searchString.includes(term))
+		},
+	})
+	const rows = table.getRowModel().rows
+
+	// Hide the table on system pages if there's no data
+	if (systemId && !zfsPools?.length && !globalFilter) {
+		return null
+	}
+
+	const openSheet = (pool: ZfsPoolRecord) => {
+		setActivePoolId(pool.id)
+		setSheetOpen(true)
+	}
+
+	return (
+		<div>
+			<Card className="@container w-full px-3 py-5 sm:py-6 sm:px-6">
+				<CardHeader className="p-0 mb-3 sm:mb-4">
+					<div className="grid md:flex gap-x-5 gap-y-3 w-full items-end">
+						<div className="px-2 sm:px-1">
+							<CardTitle className="mb-2">ZFS</CardTitle>
+							<CardDescription className="flex">
+								<Trans>Click on a pool to view vdev and dataset details.</Trans>
+							</CardDescription>
+						</div>
+						<div className="relative ms-auto w-full max-w-full md:w-64">
+							<Input
+								placeholder={t`Filter...`}
+								value={globalFilter}
+								onChange={(event) => setGlobalFilter(event.target.value)}
+								className="px-4 w-full max-w-full md:w-64"
+							/>
+							{globalFilter && (
+								<Button
+									type="button"
+									variant="ghost"
+									size="icon"
+									aria-label={t`Clear`}
+									className="absolute right-1 top-1/2 -translate-y-1/2 h-7 w-7 text-muted-foreground"
+									onClick={() => setGlobalFilter("")}
+								>
+									<XIcon className="h-4 w-4" />
+								</Button>
+							)}
+						</div>
+					</div>
+				</CardHeader>
+				<div className="h-min max-h-[calc(100dvh-17rem)] max-w-full relative overflow-auto rounded-md border">
+					<Table>
+						<TableHeader className="sticky top-0 z-50 w-full border-b-2">
+							{table.getHeaderGroups().map((headerGroup) => (
+								<TableRow key={headerGroup.id}>
+									{headerGroup.headers.map((header) => (
+										<TableHead key={header.id} className="px-2">
+											{header.isPlaceholder ? null : flexRender(header.column.columnDef.header, header.getContext())}
+										</TableHead>
+									))}
+								</TableRow>
+							))}
+						</TableHeader>
+						<TableBody>
+							{rows.map((row) => (
+								<TableRow
+									key={row.id}
+									data-state={row.getIsSelected() && "selected"}
+									className="cursor-pointer"
+									onClick={() => openSheet(row.original)}
+								>
+									{row.getVisibleCells().map((cell) => (
+										<TableCell key={cell.id}>{flexRender(cell.column.columnDef.cell, cell.getContext())}</TableCell>
+									))}
+								</TableRow>
+							))}
+						</TableBody>
+					</Table>
+				</div>
+			</Card>
+			<PoolSheet poolId={activePoolId} open={sheetOpen} onOpenChange={setSheetOpen} />
+		</div>
+	)
+}

internal/site/src/types.d.ts

@@ -151,6 +151,8 @@ export interface SystemStats {
 	f?: Record<string, number>
 	/** extra filesystems */
 	efs?: Record<string, ExtraFsStats>
+	/** ZFS pool metrics */
+	z?: Record<string, ZfsPool>
 	/** GPU data */
 	g?: Record<string, GPUData>
 	/** battery percent and state */
@@ -178,6 +180,56 @@ export interface GPUData {
 	e?: Record<string, number>
 }
 
+export interface ZfsPool {
+	/** total capacity (GiB) */
+	d: number
+	/** allocated (GiB) */
+	du: number
+	/** read throughput (bytes/s) */
+	rb?: number
+	/** write throughput (bytes/s) */
+	wb?: number
+	/** health: ONLINE, DEGRADED, FAULTED, ... */
+	h?: string
+}
+
+export interface ZfsScrub {
+	/** NONE, SCANNING, FINISHED, CANCELED */
+	state?: string
+	/** progress while scanning, e.g. "10.00%" */
+	progress?: string
+	errors?: number
+}
+
+export interface ZfsVdev {
+	name: string
+	state?: string
+	readErrs?: number
+	writeErrs?: number
+	checksumErrs?: number
+}
+
+export interface ZfsDataset {
+	name: string
+	used?: number
+	avail?: number
+	mount?: string
+}
+
+export interface ZfsPoolRecord extends RecordModel {
+	system: string
+	name: string
+	health: string
+	size: number
+	alloc: number
+	free: number
+	scrub: ZfsScrub | null
+	vdevs: ZfsVdev[] | null
+	datasets: ZfsDataset[] | null
+	details_updated: string
+	updated: string
+}
+
 export interface ExtraFsStats {
 	/** disk size (gb) */
 	d: number

readme.md

@@ -16,6 +16,7 @@ It has a friendly web interface, simple configuration, and is ready to use out o
 - **Lightweight**: Smaller and less resource-intensive than leading solutions.
 - **Simple**: Easy setup with little manual configuration required.
 - **Docker stats**: Tracks CPU, memory, and network usage history for each container.
+- **ZFS**: Tracks pool capacity, health, and I/O, plus per-dataset usage.
 - **Alerts**: Configurable alerts for CPU, memory, disk, bandwidth, temperature, fan speed, load average, and status.
 - **Multi-user**: Users manage their own systems. Admins can share systems across users.
 - **OAuth / OIDC**: Supports many OAuth2 providers. Password auth can be disabled.
@@ -53,6 +54,7 @@ The [quick start guide](https://beszel.dev/guide/getting-started) and other docu
 - **Battery** - Host system battery charge.
 - **Containers** - Status and metrics of all running Docker / Podman containers.
 - **S.M.A.R.T.** - Host system disk health (includes eMMC wear/EOL and Linux mdraid array health via sysfs when available).
+- **ZFS** - Pool capacity, usage, health, I/O throughput, scrub status, and per-dataset usage.
 
 ## Help and discussion