* admin: manage S3 bucket policies from the admin UI
Bucket policies were only manageable through the S3 PutBucketPolicy API;
the admin UI had no equivalent to the quota/owner/lifecycle editors it
already offers. Add GET/PUT/DELETE for a bucket's policy, sharing the
exact validation the S3 gateway uses.
- Extract validateBucketPolicy/validateResourceForBucket out of
s3api_bucket_policy_handlers.go into policy_engine.ValidateBucketPolicy /
ResourceMatchesBucket so both the S3 API and the admin UI enforce
identical rules.
- weed/admin/dash/bucket_policy.go: Get/Set/DeleteBucketPolicy, writing
through ObjectTransaction + PATCH_EXTENDED (the lifecycle pattern) so a
concurrent owner/quota/lifecycle change on the same bucket entry isn't
clobbered. Propagation to every S3 gateway is automatic via the existing
filer metadata log subscription. The S3 gateway's IAM policy mirror is
deliberately not replicated here (its delete path is already an
unimplemented TODO on the S3 side).
- New GET/PUT/DELETE /api/s3/buckets/{bucket}/policy routes, CSRF-guarded
on writes.
- Bucket list and details modal now show a statement-count badge, read
from the entry already fetched (no extra RPC).
- UI: a JSON-textarea policy editor modal, matching the lifecycle modal's
structure.
* admin: reuse the visual policy editor for bucket policies
Extract the structured policy editor (add/remove statement, action/
resource/principal rows with autocomplete, JSON tab kept in sync) out of
policies.templ's inline script into a shared
weed/admin/static/js/policy_editor.js, and wire the bucket policy modal
in s3_buckets.templ up to it instead of a bare JSON textarea.
- registerPolicyEditor(which, config) replaces the hardcoded create/edit
id derivation with a per-instance config (textarea/tab/body ids,
datalist ids, requirePrincipal, bucket). The IAM policies page keeps its
exact pre-extraction ids via two registerPolicyEditor calls, so its
markup is unchanged.
- New policy_datalists.templ exposes the three shared <datalist>s
(actions/resources/principals) as @PolicyDatalists(), now rendered by
both policies.templ and s3_buckets.templ.
- requirePrincipal seeds new bucket-policy statements with Principal: "*"
and adds a client-side check before save (the server, via
policy_engine.ValidateBucketPolicy, remains the actual authority); the
bucket config pins the Resource autocomplete to the open bucket instead
of fetching every bucket in the cluster.
- layout.templ loads policy_editor.js globally, after admin.js/
modal-alerts.js (basePath/escapeHtml/showAlert) which it depends on.
3a (the extraction) is a byte-preserving move verified against the
unchanged policies.templ behavior before layering 3b's parameterization
and the bucket-policy wiring on top.
* admin: migrate S3 Tables bucket/table policy editors to the shared editor
Third consumer of the shared visual policy editor: the S3 Tables bucket
and table policy modals (a bare JSON textarea each) now get the same
structured Editor/JSON tabs as the bucket policy and IAM policy pages,
via registerPolicyEditor('s3tablesBucketPolicy'/'s3tablesTablePolicy',
{ textareaId: ... }). Storage and validation are untouched - S3 Tables
policies still go through their own s3tables.PolicyDocument type and the
s3tables.policy extended attribute, unrelated to policy_engine and
s3-bucket-policy; only the editor UI is shared.
Fix a real bug surfaced by adding this second load path: the bucket
policy modal (and the naive first draft of this s3tables port) called
commitPolicyTextareaToEditor() right after a GET and then force-switched
to the Editor tab. commitPolicyTextareaToEditor() is designed to leave
the current tab in place and the editor state untouched when a document
fails to parse (so an in-progress edit survives a bad tab switch), so
forcing the Editor tab afterwards could show empty/stale editor state
that a careless Save would then serialize over a perfectly valid but
structurally-unusual stored policy. Add
loadPolicyTextareaIntoEditor(which) to policy_editor.js, which has no
"current tab" to defer to and instead falls back to the JSON tab with an
alert on a document the structured editor can't represent - the same
safety editPolicy already had in policies.templ - and use it at all three
"populate the editor right after a GET" call sites (bucket policy,
S3 Tables bucket policy, S3 Tables table policy).
* admin: show policy statement count on the S3 Tables buckets page
Mirrors the "Policy" column already added to the classic S3 buckets
list: a clickable badge with the statement count when the table bucket
has a resource policy, "Not configured" otherwise. S3 Tables policies
are a separate mechanism (s3tables.PolicyDocument under the
s3tables.policy extended attribute) from the S3 bucket policy work
elsewhere in this branch (policy_engine.PolicyDocument /
s3-bucket-policy), so this is a parallel implementation of the same
pattern rather than shared code.
- S3TablesBucketSummary gains PolicyStatementCount, populated in
GetS3TablesBucketsData from entry.Entry.Extended[s3tables.ExtendedKeyPolicy]
via the new extractS3TablesPolicyStatementCountFromEntry - no extra RPC,
the entry is already fetched for ExtendedKeyMetadata.
- The badge reuses the existing .s3tables-bucket-policy-btn class, so it
opens the same policy modal as the row's action button with no JS
changes.
* admin: don't let a failed policy GET open the door to an empty overwrite
loadS3TablesBucketPolicy/loadS3TablesTablePolicy cleared the textarea,
then unconditionally called loadPolicyTextareaIntoEditor() regardless of
whether the GET actually succeeded - including when fetch() rejected or
the response was not ok, silently logged to console only. That leaves
the structured editor holding a legitimate-looking empty policy
({version, statements: []}), with the Editor tab active by default.
If Save is then clicked, commitPolicyActiveTab() serializes that empty
state into the textarea as `{"Version":"2012-10-17","Statement":[]}` -
a non-empty string - before the "Policy JSON is required" guard ever
sees it, so the guard passes and the transient load failure gets
written over whatever policy was actually stored.
Add s3tablesBucketPolicyLoaded/s3tablesTablePolicyLoaded, set true only
once a GET has actually completed (ok, including a genuinely empty
policy) and false on any failure path (fetch rejection or a non-ok
response, which previously fell through silently). Both submit handlers
now check the flag before touching the editor at all, and a failed load
surfaces via alert() instead of only a console.error - the user
previously had no visible indication the load had failed.
Verified with a jsdom simulation driving the real rendered page against
a stubbed fetch: a failed GET followed by Save now sends no PUT at all
(previously it sent Statement: []); a successful GET followed by Save
still PUTs the loaded policy unchanged.
* admin: address code review findings on the policy editor
1. policy_editor.js: policyEditors is only pre-populated for 'create'/
'edit'; every other `which` (bucket, s3tablesBucket, s3tablesTable)
stays undefined until its first successful async load. Nothing in
this file enforces that a page hide its Editor/JSON tabs and
Add-statement button until that load completes - the S3 Tables policy
modals don't - so a click in that window (e.g. Add statement, or
switching to the JSON tab) threw "Cannot read properties of undefined
(reading 'unparsed')". Add policyEditorState(which), which lazily
initializes a default state, and route addPolicyStatement, the
jsonTabBtn 'show.bs.tab' handler, commitPolicyActiveTab, and
renderPolicyEditor through it. Verified with a jsdom simulation
against a never-resolving fetch: the exact click threw on the
pre-fix code and no longer does.
2. s3_buckets.templ: the bucket-policy Save handler checked the
textarea for emptiness before calling commitPolicyActiveTab(), which
is what actually serializes the structured Editor tab's fields into
that textarea. A policy entered entirely through the Editor tab (the
primary path - never touching the JSON tab) left the textarea at
whatever it was at load time, so creating a new policy this way hit
"Enter a policy document" and Save silently did nothing. Move the
commit before the emptiness check, preserving the existing alert and
early-return. Verified with a jsdom simulation: Add-statement then
Save (no tab switch) now PUTs the entered statement; before the fix
the same sequence never reached fetch().
3. s3tables_buckets.templ / s3tables_tables.templ: the policy Editor/
JSON nav-tabs were missing the ARIA roles Bootstrap's own tab pattern
expects (role="tab"/"tabpanel", aria-selected, aria-controls,
aria-labelledby) - screen readers had no way to tell these were tabs
or which pane went with which button. Added the standard Bootstrap 5
tab markup to both.
* admin: guard policy load/save flows against overlapping requests
1. s3tables.js: loadS3TablesBucketPolicy/loadS3TablesTablePolicy had no
protection against overlapping loads. Opening one bucket's (or
table's) policy dialog and then another's before the first GET
resolved let the late response write its document into the shared
textarea and mark the dialog "loaded" while it was now targeting the
second resource - a subsequent Save would then push the first
resource's policy onto the second. Add a per-load monotonic sequence
number (s3tablesBucketPolicyRequestSeq / s3tablesTablePolicyRequestSeq,
the same pattern already used for the classic bucket-policy load in
s3_buckets.templ); a response is only applied - textarea, loaded flag,
editor state - if its captured sequence still matches the latest one
issued.
Verified with a jsdom simulation: bucket A's policy load (artificially
slow) followed immediately by bucket B's (fast) previously left A's
policy in the textarea once A's late response landed; it now correctly
keeps B's.
2. s3_buckets.templ: the bucket-policy Save button lives outside the
(initially hidden) editor wrapper, so it stays clickable while a load
is still in flight - the existing policyRequestSeq guard only protects
the *load* from a stale response, not Save from firing before any
load for the current bucket has completed. Add bucketPolicyLoaded,
reset before each GET and set only once the matching response lands,
and check it at the top of the Save handler.
Verified with a jsdom simulation: clicking Save immediately after
opening the dialog, before a (deliberately never-resolving) GET
settles, now sends no PUT; a normal load-then-save sequence still
PUTs the loaded policy unchanged.
* admin: address further code review findings on the policy editor
1. s3tables.js: loadS3TablesBucketPolicy/loadS3TablesTablePolicy only
reset the JSON textarea when a new load starts; the structured editor
kept showing the previously loaded resource's statements (Editor tab
is the default active one) until the new fetch resolved. Call
loadPolicyTextareaIntoEditor() against the now-cleared textarea
immediately, so switching resources visibly resets the editor right
away instead of only once its own load completes. Verified with jsdom:
opening bucket A (loads fully) then bucket B (GET never resolves) no
longer leaves A's statements visible in B's editor.
2. s3tables.js: deleteS3TablesBucketPolicy/deleteS3TablesTablePolicy had
no loaded-state check, so a failed GET (which already blocks Save)
left Delete fully able to remove the resource's stored policy sight
unseen. Add the same s3tablesBucketPolicyLoaded/s3tablesTablePolicyLoaded
guard Save already uses. Verified with jsdom: delete after a failed
load now sends no DELETE; delete after a successful load is unaffected.
3. s3_buckets.templ: the bucket-policy Editor/JSON nav-tabs were missing
the same ARIA roles already added to the S3 Tables policy tabs in an
earlier round (role="tab"/"tabpanel", aria-selected, aria-controls,
aria-labelledby) - this instance was out of scope for that review
comment but is the same gap. Bootstrap's own tab.js already manages
aria-selected on tab switch once the attribute exists, so no extra JS
was needed.
4. s3_buckets.templ: neither the bucket-policy Save nor Delete handler
guarded against a double-click, or against firing while the other was
still in flight - two overlapping PUT/DELETE requests for the same
bucket could land in either order. Add a shared
bucketPolicyMutationInFlight flag: set (and both buttons disabled)
before each fetch, cleared (and buttons re-enabled) on failure so the
user can retry, left set through the existing success hide-and-reload
path, and also reset when a new bucket's dialog opens so an abandoned
in-flight request from a closed dialog can't leave the buttons stuck
disabled. Verified with jsdom: double-clicking Save now sends exactly
one PUT, and a Delete click while that PUT is still pending sends no
DELETE.
* admin: scope bucket-policy mutation completions to the bucket that started them
1. The previous round's fix reset bucketPolicyMutationInFlight whenever a
new bucket's policy dialog opened, to avoid leaving Save/Delete stuck
disabled if the modal was closed mid-request. That traded one bug for
a worse one: if bucket A's PUT/DELETE was still in flight when the
user opened bucket B's dialog, the reset let B's Save/Delete fire
immediately, and A's completion handler - unaware anything had
changed - would still hide the (now B's) modal and reload the page
out from under whatever the user was doing with B, on success, or
alert a message with no bucket context, on failure.
Stop resetting on reopen, so a pending mutation for a previous bucket
keeps this bucket's Save/Delete blocked until it settles (matches the
"preventing overlapping mutations" the review comment describes).
Instead, capture policyEditorBucket as targetBucket right before each
fetch and compare it against policyEditorBucket again in the
completion handler: the in-flight flag is always released so the
buttons never get stuck, but the modal-hide/reload/alert only fire if
this bucket is still the one showing; a stale completion for an
abandoned bucket just logs to the console instead.
Verified with a jsdom simulation: opening bucket B while bucket A's
Save is still pending leaves B's Save button disabled and a click on
it a no-op; once A's PUT resolves, B's button re-enables but no
modal.hide()/reload() fires (previously both fired unconditionally).
2. bucketPolicyDeleteBtn had no bucketPolicyLoaded check, unlike Save -
a failed GET blocked Save but left Delete free to remove a policy the
client never actually saw (the same gap already fixed for the S3
Tables policy modals in an earlier round). Added the same guard,
ahead of the confirm() dialog. Verified with jsdom: Delete after a
failed load now sends no DELETE request.
* admin: fix spelling mistake
SeaweedFS
Sponsor SeaweedFS via Patreon
SeaweedFS is an independent Apache-licensed open source project with its ongoing development made possible entirely thanks to the support of these awesome backers. If you'd like to grow SeaweedFS even stronger, please consider joining our sponsors on Patreon.
Your support will be really appreciated by me and other supporters!
Gold Sponsors
- Download Binaries for different platforms
- SeaweedFS on Slack
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- SeaweedFS on Reddit
- SeaweedFS Mailing List
- Wiki Documentation
- SeaweedFS White Paper
- SeaweedFS Introduction Slides 2025.5
- SeaweedFS Introduction Slides 2021.5
- SeaweedFS Introduction Slides 2019.3
Table of Contents
- Quick Start
- Introduction
- Features
- Example: Using Seaweed Blob Store
- Architecture
- Compared to Other File Systems
- Dev Plan
- Installation Guide
- Disk Related Topics
- Benchmark
- Enterprise
- License
Quick Start
Quick Start with weed mini
Download the latest binary from https://github.com/seaweedfs/seaweedfs/releases and unzip the single weed (or weed.exe) file, or run go install github.com/seaweedfs/seaweedfs/weed@latest. Then start a ready-to-use S3 object store with credentials and a pre-created bucket in one command:
AWS_ACCESS_KEY_ID=admin \
AWS_SECRET_ACCESS_KEY=secret \
S3_BUCKET=my-bucket \
./weed mini -dir=/data
That's it — the S3 endpoint is at http://localhost:8333, my-bucket already exists, and admin/secret are valid credentials. S3_BUCKET accepts a comma-separated list (e.g. raw,processed); use S3_TABLE_BUCKET for S3 Tables buckets, each name or name:FORMAT where the format is ICEBERG (the default) or LANCE. Drop any of the env vars to skip that piece (no AWS keys → S3 runs in unauthenticated "Allow All" mode for development).
The same command starts everything else too:
- S3 Endpoint: http://localhost:8333
- Master UI: http://localhost:9333
- Volume Server: http://localhost:9340
- Filer UI: http://localhost:8888
- WebDAV: http://localhost:7333
- Admin UI: http://localhost:23646
macOS: if the binary is quarantined, run
xattr -d com.apple.quarantine ./weedfirst.
Perfect for development, testing, learning SeaweedFS, and single-node deployments. To scale out, add more volume servers by running weed volume -dir="/some/data/dir2" -master="<master_host>:9333" -port=8081 locally, on another machine, or on thousands of machines.
Quick Start for S3 API on Docker
docker run -p 8333:8333 \
-e AWS_ACCESS_KEY_ID=admin \
-e AWS_SECRET_ACCESS_KEY=secret \
-e S3_BUCKET=my-bucket \
chrislusf/seaweedfs
Same behavior as the weed mini command above — the S3 endpoint is at http://localhost:8333 with my-bucket pre-created. Drop the env vars to run anonymously for development.
Introduction
SeaweedFS is a simple and highly scalable distributed file system. There are two objectives:
- to store billions of files!
- to serve the files fast!
SeaweedFS started as a blob store to handle small files efficiently. Instead of managing all file metadata in a central master, the central master only manages volumes on volume servers, and these volume servers manage files and their metadata. This relieves concurrency pressure from the central master and spreads file metadata into volume servers, allowing faster file access (O(1), usually just one disk read operation).
There is only 40 bytes of disk storage overhead for each file's metadata. It is so simple with O(1) disk reads that you are welcome to challenge the performance with your actual use cases.
SeaweedFS started by implementing Facebook's Haystack design paper. Also, SeaweedFS implements erasure coding with ideas from f4: Facebook’s Warm BLOB Storage System, and has a lot of similarities with Facebook’s Tectonic Filesystem and Google's Colossus File System
On top of the blob store, optional Filer can support directories and POSIX attributes. Filer is a separate linearly-scalable stateless server with customizable metadata stores, e.g., MySql, Postgres, Redis, Cassandra, HBase, Mongodb, Elastic Search, LevelDB, RocksDB, Sqlite, MemSql, TiDB, Etcd, CockroachDB, YDB, etc.
SeaweedFS can transparently integrate with the cloud. With hot data on local cluster, and warm data on the cloud with O(1) access time, SeaweedFS can achieve both fast local access time and elastic cloud storage capacity. What's more, the cloud storage access API cost is minimized. Faster and cheaper than direct cloud storage!
SeaweedFS also ships a built-in Iceberg REST Catalog, turning the same cluster into a self-contained lakehouse. Spark, Trino, Dremio, DuckDB, and RisingWave can query Iceberg tables directly — no Hive Metastore, Glue, or external catalog service required. Storage and table metadata live in one system, simplifying on-prem and small-team analytics stacks.
Features
Additional Blob Store Features
- Support different replication levels, with rack and data center aware.
- Automatic master servers failover - no single point of failure (SPOF).
- Automatic compression depending on file MIME type.
- Automatic compaction to reclaim disk space after deletion or update.
- Automatic entry TTL expiration.
- Flexible Capacity Expansion: Any server with some disk space can add to the total storage space.
- Adding/Removing servers does not cause any data re-balancing unless triggered by admin commands.
- Optional picture resizing.
- Support ETag, Accept-Range, Last-Modified, etc.
- Support in-memory/leveldb/readonly mode tuning for memory/performance balance.
- Support rebalancing the writable and readonly volumes.
- Customizable Multiple Storage Tiers: Customizable storage disk types to balance performance and cost.
- Transparent cloud integration: unlimited capacity via tiered cloud storage for warm data.
- Erasure Coding for warm storage Rack-Aware 10.4 erasure coding reduces storage cost and increases availability. Enterprise version can customize EC ratio.
Filer Features
- Filer server provides "normal" directories and files via HTTP.
- File TTL automatically expires file metadata and actual file data.
- Mount filer reads and writes files directly as a local directory via FUSE.
- Filer Store Replication enables HA for filer meta data stores.
- Active-Active Replication enables asynchronous one-way or two-way cross cluster continuous replication.
- Amazon S3 compatible API accesses files with S3 tooling.
- Hadoop Compatible File System accesses files from Hadoop/Spark/Flink/etc or even runs HBase.
- Async Replication To Cloud has extremely fast local access and backups to Amazon S3, Google Cloud Storage, Azure, BackBlaze.
- WebDAV accesses as a mapped drive on Mac and Windows, or from mobile devices.
- AES256-GCM Encrypted Storage safely stores the encrypted data.
- Super Large Files stores large or super large files in tens of TB.
- Cloud Drive mounts cloud storage to local cluster, cached for fast read and write with asynchronous write back.
- Gateway to Remote Object Store mirrors bucket operations to remote object storage, in addition to Cloud Drive
Data Lakehouse Features
- S3 Table Buckets expose a dedicated namespace for Iceberg tables with strict layout validation.
- Built-in Iceberg REST Catalog runs alongside the S3 endpoint — no external metastore needed.
- Native integrations with Apache Spark, Trino, Dremio, DuckDB, and RisingWave.
- Automated table maintenance: compaction, snapshot expiration, orphan removal, manifest rewriting.
- Granular IAM at the bucket, namespace, and table level via standard S3 bucket policies.
Kubernetes
- Kubernetes CSI Driver A Container Storage Interface (CSI) Driver.
- SeaweedFS Operator
Example: Using Seaweed Blob Store
By default, the master node runs on port 9333, and the volume nodes run on port 8080. Let's start one master node, and two volume nodes on port 8080 and 8081. Ideally, they should be started from different machines. We'll use localhost as an example.
SeaweedFS uses HTTP REST operations to read, write, and delete. The responses are in JSON or JSONP format.
Start Master Server
> ./weed master
Start Volume Servers
> weed volume -dir="/tmp/data1" -max=5 -master="localhost:9333" -port=8080 &
> weed volume -dir="/tmp/data2" -max=10 -master="localhost:9333" -port=8081 &
Write A Blob
A blob, also referred as a needle, a chunk, or mistakenly as a file, is just a byte array. It can have attributes, such as name, mime type, create or update time, etc. But basically it is just a byte array of a relatively small size, such as 2 MB ~ 64 MB. The size is not fixed.
To upload a blob: first, send a HTTP POST, PUT, or GET request to /dir/assign to get an fid and a volume server URL:
> curl http://localhost:9333/dir/assign
{"count":1,"fid":"3,01637037d6","url":"127.0.0.1:8080","publicUrl":"localhost:8080"}
Second, to store the blob content, send a HTTP multi-part POST request to url + '/' + fid from the response:
> curl -F file=@/home/chris/myphoto.jpg http://127.0.0.1:8080/3,01637037d6
{"name":"myphoto.jpg","size":43234,"eTag":"1cc0118e"}
To update, send another POST request with updated blob content.
For deletion, send an HTTP DELETE request to the same url + '/' + fid URL:
> curl -X DELETE http://127.0.0.1:8080/3,01637037d6
Save Blob Id
Now, you can save the fid, 3,01637037d6 in this case, to a database field.
The number 3 at the start represents a volume id. After the comma, it's one file key, 01, and a file cookie, 637037d6.
The volume id is an unsigned 32-bit integer. The file key is an unsigned 64-bit integer. The file cookie is an unsigned 32-bit integer, used to prevent URL guessing.
The file key and file cookie are both coded in hex. You can store the <volume id, file key, file cookie> tuple in your own format, or simply store the fid as a string.
If stored as a string, in theory, you would need 8+1+16+8=33 bytes. A char(33) would be enough, if not more than enough, since most uses will not need 2^32 volumes.
If space is really a concern, you can store the file id in the binary format. You would need one 4-byte integer for volume id, 8-byte long number for file key, and a 4-byte integer for the file cookie. So 16 bytes are more than enough.
Read a Blob
Here is an example of how to render the URL.
First look up the volume server's URLs by the file's volumeId:
> curl http://localhost:9333/dir/lookup?volumeId=3
{"volumeId":"3","locations":[{"publicUrl":"localhost:8080","url":"localhost:8080"}]}
Since (usually) there are not too many volume servers, and volumes don't move often, you can cache the results most of the time. Depending on the replication type, one volume can have multiple replica locations. Just randomly pick one location to read.
Now you can take the public URL, render the URL or directly read from the volume server via URL:
http://localhost:8080/3,01637037d6.jpg
Notice we add a file extension ".jpg" here. It's optional and just one way for the client to specify the file content type.
If you want a nicer URL, you can use one of these alternative URL formats:
http://localhost:8080/3/01637037d6/my_preferred_name.jpg
http://localhost:8080/3/01637037d6.jpg
http://localhost:8080/3,01637037d6.jpg
http://localhost:8080/3/01637037d6
http://localhost:8080/3,01637037d6
If you want to get a scaled version of an image, you can add some params:
http://localhost:8080/3/01637037d6.jpg?height=200&width=200
http://localhost:8080/3/01637037d6.jpg?height=200&width=200&mode=fit
http://localhost:8080/3/01637037d6.jpg?height=200&width=200&mode=fill
Rack-Aware and Data Center-Aware Replication
SeaweedFS applies the replication strategy at a volume level. So, when you are getting a blob id, you can specify the replication strategy. For example:
curl http://localhost:9333/dir/assign?replication=001
The replication parameter options are:
000: no replication
001: replicate once on the same rack
010: replicate once on a different rack, but same data center
100: replicate once on a different data center
200: replicate twice on two different data center
110: replicate once on a different rack, and once on a different data center
More details about replication can be found on the wiki.
You can also set the default replication strategy when starting the master server.
Allocate Blob Key on Specific Data Center
Volume servers can be started with a specific data center name:
weed volume -dir=/tmp/1 -port=8080 -dataCenter=dc1
weed volume -dir=/tmp/2 -port=8081 -dataCenter=dc2
When requesting a blob key, an optional "dataCenter" parameter can limit the assigned volume to the specific data center. For example, this specifies that the assigned volume should be limited to 'dc1':
http://localhost:9333/dir/assign?dataCenter=dc1
Other Features
- No Single Point of Failure
- Insert with your own keys
- Chunking large files
- Collection as a Simple Name Space
Blob Store Architecture
Usually distributed file systems split each file into chunks. A central server keeps a mapping of filenames to chunks, and also which chunks each chunk server has.
The main drawback is that the central server can't handle many small files efficiently, and since all read requests need to go through the central master, so it might not scale well for many concurrent users.
Instead of managing chunks, SeaweedFS manages data volumes in the master server. Each data volume is 32GB in size, and can hold a lot of blobs. And each storage node can have many data volumes. So the master node only needs to store the metadata about the volumes, which is a fairly small amount of data and is generally stable.
The actual blob metadata, which are the blob volume, offset, and size, is stored in each volume on volume servers. Since each volume server only manages metadata of blobs on its own disk, with only 16 bytes for each blob, all access can read the metadata just from memory and only needs one disk operation to actually read file data.
For comparison, consider that an xfs inode structure in Linux is 536 bytes.
Master Server and Volume Server
The architecture is fairly simple. The actual data is stored in volumes on storage nodes. One volume server can have multiple volumes, and can both support read and write access with basic authentication.
All volumes are managed by a master server. The master server contains the volume id to volume server mapping. This is fairly static information, and can be easily cached.
On each write request, the master server also generates a file key, which is a growing 64-bit unsigned integer. Since write requests are not generally as frequent as read requests, one master server should be able to handle the concurrency well.
Write and Read files
When a client sends a write request, the master server returns (volume id, file key, file cookie, volume node URL) for the blob. The client then contacts the volume node and POSTs the blob content.
When a client needs to read a blob based on (volume id, file key, file cookie), it asks the master server by the volume id for the (volume node URL, volume node public URL), or retrieves this from a cache. Then the client can GET the content, or just render the URL on web pages and let browsers fetch the content.
Saving memory
All blob metadata stored on a volume server is readable from memory without disk access. Each file takes just a 16-byte map entry of <64bit key, 32bit offset, 32bit size>. Of course, each map entry has its own space cost for the map. But usually the disk space runs out before the memory does.
Tiered Storage to the cloud
The local volume servers are much faster, while cloud storages have elastic capacity and are actually more cost-efficient if not accessed often (usually free to upload, but relatively costly to access). With the append-only structure and O(1) access time, SeaweedFS can take advantage of both local and cloud storage by offloading the warm data to the cloud.
Usually hot data are fresh and warm data are old. SeaweedFS puts the newly created volumes on local servers, and optionally upload the older volumes on the cloud. If the older data are accessed less often, this literally gives you unlimited capacity with limited local servers, and still fast for new data.
With the O(1) access time, the network latency cost is kept at minimum.
If the hot/warm data is split as 20/80, with 20 servers, you can achieve storage capacity of 100 servers. That's a cost saving of 80%! Or you can repurpose the 80 servers to store new data also, and get 5X storage throughput.
SeaweedFS Filer
Built on top of the blob store, SeaweedFS Filer adds directory structure to create a file system. The directory structure is an interface that is implemented in many key-value stores or databases.
The content of a file is mapped to one or many blobs, distributed to multiple volumes on multiple volume servers.
Compared to Other File Systems
Most other distributed file systems seem more complicated than necessary.
SeaweedFS is meant to be fast and simple, in both setup and operation. If you do not understand how it works when you reach here, we've failed! Please raise an issue with any questions or update this file with clarifications.
SeaweedFS is constantly moving forward. Same with other systems. These comparisons can be outdated quickly. Please help to keep them updated.
Compared to HDFS
HDFS uses the chunk approach for each file, and is ideal for storing large files.
SeaweedFS is ideal for serving relatively smaller files quickly and concurrently.
SeaweedFS can also store extra large files by splitting them into manageable data chunks, and store the file ids of the data chunks into a meta chunk. This is managed by "weed upload/download" tool, and the weed master or volume servers are agnostic about it.
Compared to GlusterFS, Ceph
The architectures are mostly the same. SeaweedFS aims to store and read files fast, with a simple and flat architecture. The main differences are
- SeaweedFS optimizes for small files, ensuring O(1) disk seek operation, and can also handle large files.
- SeaweedFS statically assigns a volume id for a file. Locating file content becomes just a lookup of the volume id, which can be easily cached.
- SeaweedFS Filer metadata store can be any well-known and proven data store, e.g., Redis, Cassandra, HBase, Mongodb, Elastic Search, MySql, Postgres, Sqlite, MemSql, TiDB, CockroachDB, Etcd, YDB etc, and is easy to customize.
- SeaweedFS Volume server also communicates directly with clients via HTTP, supporting range queries, direct uploads, etc.
| System | File Metadata | File Content Read | POSIX | REST API | Optimized for large number of small files |
|---|---|---|---|---|---|
| SeaweedFS | lookup volume id, cacheable | O(1) disk seek | Yes | Yes | |
| SeaweedFS Filer | Linearly Scalable, Customizable | O(1) disk seek | FUSE | Yes | Yes |
| GlusterFS | hashing | FUSE, NFS | |||
| Ceph | hashing + rules | FUSE | Yes | ||
| MooseFS | in memory | FUSE | No | ||
| MinIO | separate meta file per drive for each file | Yes | No | ||
| RustFS | separate meta file per drive for each file | Yes | No |
Compared to GlusterFS
GlusterFS stores files, both directories and content, in configurable volumes called "bricks".
GlusterFS hashes the path and filename into ids, and assigned to virtual volumes, and then mapped to "bricks".
Compared to MooseFS
MooseFS chooses to neglect small file issue. From moosefs 3.0 manual, "even a small file will occupy 64KiB plus additionally 4KiB of checksums and 1KiB for the header", because it "was initially designed for keeping large amounts (like several thousands) of very big files"
MooseFS Master Server keeps all meta data in memory. Same issue as HDFS namenode.
Compared to Ceph
Ceph can be setup similar to SeaweedFS as a key->blob store. It is much more complicated, with the need to support layers on top of it. Here is a more detailed comparison
SeaweedFS has a centralized master group to look up free volumes, while Ceph uses hashing and metadata servers to locate its objects. Having a centralized master makes it easy to code and manage.
Ceph, like SeaweedFS, is based on the object store RADOS. Ceph is rather complicated with mixed reviews.
Ceph uses CRUSH hashing to automatically manage data placement, which is efficient to locate the data. But the data has to be placed according to the CRUSH algorithm. Any wrong configuration would cause data loss. Topology changes, such as adding new servers to increase capacity, will cause data migration with high IO cost to fit the CRUSH algorithm. SeaweedFS places data by assigning them to any writable volumes. If writes to one volume failed, just pick another volume to write. Adding more volumes is also as simple as it can be.
SeaweedFS is optimized for small files. Small files are stored as one continuous block of content, with at most 8 unused bytes between files. Small file access is O(1) disk read.
SeaweedFS Filer uses off-the-shelf stores, such as MySql, Postgres, Sqlite, Mongodb, Redis, Elastic Search, Cassandra, HBase, MemSql, TiDB, CockroachCB, Etcd, YDB, to manage file directories. These stores are proven, scalable, and easier to manage.
| SeaweedFS | comparable to Ceph | advantage |
|---|---|---|
| Master | MDS | simpler |
| Volume | OSD | optimized for small files |
| Filer | Ceph FS | linearly scalable, Customizable, O(1) or O(logN) |
Compared to MinIO, RustFS
Please note, as Apr 25, 2026 MinIO ceased development. It's strongly discouraged to use that unmaintained software with multiple security bugs. RustFS is a MinIO reimplementation in Rust, Apache 2.0 licensed and still developed, keeping MinIO's storage model down to a byte-compatible on-disk format. So the points below apply to both.
MinIO followed AWS S3 closely and was ideal for testing for S3 API. It had good UI, policies, versionings, etc. SeaweedFS is trying to catch up here.
The metadata are in simple files. Each file write incurs extra writes to the corresponding meta file, on every drive of the erasure set. Changing only tags or retention rewrites that meta file on all of them, so the write amplification does not shrink with object size.
There is no optimization for lots of small files. The files are simply stored as is to local disks. Plus the extra meta file and shards for erasure coding, it only amplifies the LOSF problem.
Multiple disk IO are needed to read one file. SeaweedFS has O(1) disk reads, even for erasure coded files.
Erasure coding is full-time. SeaweedFS uses replication on hot data for faster speed and optionally applies erasure coding on warm data.
No POSIX-like API support.
There are specific requirements on storage layout, which makes it hard to scale out and to maintain. An erasure set must be 2 to 16 drives and must divide the drive list symmetrically, and capacity grows or shrinks a whole pool at a time. In SeaweedFS, just start one volume server pointing to the master. That's all.
Dev Plan
- More tools and documentation, on how to manage and scale the system.
- Read and write stream data.
- Support structured data.
This is a super exciting project! And we need helpers and support!
Installation Guide
Installation guide for users who are not familiar with golang
Step 1: install go on your machine and setup the environment by following the instructions at:
https://golang.org/doc/install
make sure to define your $GOPATH
Step 2: checkout this repo:
git clone https://github.com/seaweedfs/seaweedfs.git
Step 3: download, compile, and install the project by executing the following command
cd seaweedfs/weed && make install
Once this is done, you will find the executable "weed" in your $GOPATH/bin directory
For more installation options, including how to run with Docker, see the Getting Started guide.
Disk Related Topics
Hard Drive Performance
When testing read performance on SeaweedFS, it basically becomes a performance test of your hard drive's random read speed. Hard drives usually get 100MB/s~200MB/s.
Solid State Disk
To modify or delete small files, SSD must delete a whole block at a time, and move content in existing blocks to a new block. SSD is fast when brand new, but will get fragmented over time and you have to garbage collect, compacting blocks. SeaweedFS is friendly to SSD since it is append-only. Deletion and compaction are done on volume level in the background, not slowing reading and not causing fragmentation.
Benchmark
My Own Unscientific Single Machine Results on Mac Book with Solid State Disk, CPU: 1 Intel Core i7 2.6GHz.
Write 1 million 1KB file:
Concurrency Level: 16
Time taken for tests: 66.753 seconds
Completed requests: 1048576
Failed requests: 0
Total transferred: 1106789009 bytes
Requests per second: 15708.23 [#/sec]
Transfer rate: 16191.69 [Kbytes/sec]
Connection Times (ms)
min avg max std
Total: 0.3 1.0 84.3 0.9
Percentage of the requests served within a certain time (ms)
50% 0.8 ms
66% 1.0 ms
75% 1.1 ms
80% 1.2 ms
90% 1.4 ms
95% 1.7 ms
98% 2.1 ms
99% 2.6 ms
100% 84.3 ms
Randomly read 1 million files:
Concurrency Level: 16
Time taken for tests: 22.301 seconds
Completed requests: 1048576
Failed requests: 0
Total transferred: 1106812873 bytes
Requests per second: 47019.38 [#/sec]
Transfer rate: 48467.57 [Kbytes/sec]
Connection Times (ms)
min avg max std
Total: 0.0 0.3 54.1 0.2
Percentage of the requests served within a certain time (ms)
50% 0.3 ms
90% 0.4 ms
98% 0.6 ms
99% 0.7 ms
100% 54.1 ms
Run WARP and launch a mixed benchmark.
make benchmark
warp: Benchmark data written to "warp-mixed-2025-12-05[194844]-kBpU.csv.zst"
Mixed operations.
Operation: DELETE, 10%, Concurrency: 20, Ran 42s.
* Throughput: 55.13 obj/s
Operation: GET, 45%, Concurrency: 20, Ran 42s.
* Throughput: 2477.45 MiB/s, 247.75 obj/s
Operation: PUT, 15%, Concurrency: 20, Ran 42s.
* Throughput: 825.85 MiB/s, 82.59 obj/s
Operation: STAT, 30%, Concurrency: 20, Ran 42s.
* Throughput: 165.27 obj/s
Cluster Total: 3302.88 MiB/s, 550.51 obj/s over 43s.
Enterprise
For enterprise users, please visit seaweedfs.com for the SeaweedFS Enterprise Edition, which has advanced features, including data recovery, self-healing storage, customizable erasure coding, EC vacuum and repair, etc.
License
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
The text of this page is available for modification and reuse under the terms of the Creative Commons Attribution-Sharealike 3.0 Unported License and the GNU Free Documentation License (unversioned, with no invariant sections, front-cover texts, or back-cover texts).




