mirror of
https://github.com/SCST-project/scst.git
synced 2026-05-23 13:41:27 +00:00
bb7f5caef2
svn+ssh://yanb123@svn.code.sf.net/p/scst/svn/trunk
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r5875 | bvassche | 2014-11-16 19:58:07 +0200 (Sun, 16 Nov 2014) | 1 line
nightly build: Update kernel versions
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r5878 | bvassche | 2014-11-19 02:17:41 +0200 (Wed, 19 Nov 2014) | 1 line
srpt/Makefile: Add double quotes around a path
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r5879 | bvassche | 2014-11-19 02:20:20 +0200 (Wed, 19 Nov 2014) | 1 line
scripts/generate-release-archive: Accept an optional list of file names
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r5880 | bvassche | 2014-11-22 13:12:29 +0200 (Sat, 22 Nov 2014) | 1 line
nightly build: Update kernel versions
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r5881 | bvassche | 2014-11-24 19:59:14 +0200 (Mon, 24 Nov 2014) | 4 lines
ib_srpt: Add support for HCA's that do not support SRQ
Based on a patch provided by Parav Pandit <Parav.Pandit@Emulex.Com>
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r5882 | vlnb | 2014-11-26 09:02:17 +0200 (Wed, 26 Nov 2014) | 3 lines
Update for kernels 3.17.x
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r5883 | bvassche | 2014-11-26 10:05:09 +0200 (Wed, 26 Nov 2014) | 1 line
Add kernel 3.17 build infrastructure
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r5884 | bvassche | 2014-11-26 10:07:08 +0200 (Wed, 26 Nov 2014) | 1 line
nightly build: Add kernel 3.17
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r5885 | bvassche | 2014-11-26 10:16:44 +0200 (Wed, 26 Nov 2014) | 6 lines
Fix kernel 3.17 checkpatch warnings about 'long long unsigned'
Avoid that checkpatch reports the following warning:
WARNING: type 'long long unsigned' should be specified in 'unsigned long long' order.
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r5886 | bvassche | 2014-11-26 15:38:52 +0200 (Wed, 26 Nov 2014) | 1 line
Build fixes for RHEL 6.6 kernel 2.6.32-504
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r5887 | bvassche | 2014-11-26 16:39:51 +0200 (Wed, 26 Nov 2014) | 1 line
ib_srpt: Make the send queue full messages more informational
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r5888 | bvassche | 2014-11-26 18:25:57 +0200 (Wed, 26 Nov 2014) | 1 line
scripts/specialize-patch: Support blanks around numbers inside parentheses
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r5889 | bvassche | 2014-11-26 21:42:10 +0200 (Wed, 26 Nov 2014) | 1 line
scripts/specialize-patch: Reduce noise in nightly build output
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r5890 | vlnb | 2014-11-27 06:36:33 +0200 (Thu, 27 Nov 2014) | 3 lines
Cleanup
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r5891 | bvassche | 2014-11-27 17:18:58 +0200 (Thu, 27 Nov 2014) | 1 line
scst.h: Add uintptr_t
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r5892 | bvassche | 2014-11-27 17:19:21 +0200 (Thu, 27 Nov 2014) | 1 line
ib_srpt: Add support for immediate data
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r5893 | bvassche | 2014-11-27 17:24:17 +0200 (Thu, 27 Nov 2014) | 1 line
ib_srpt: Log reject reason
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r5894 | bvassche | 2014-11-27 17:29:29 +0200 (Thu, 27 Nov 2014) | 1 line
ib_srpt: Rework the max_sge computation changes from r5795
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r5895 | bvassche | 2014-11-28 11:16:37 +0200 (Fri, 28 Nov 2014) | 1 line
scst: Add scripts/rebuild-rhel-kernel-rpm to the SCST release archive
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r5903 | bvassche | 2014-12-03 13:50:06 +0200 (Wed, 03 Dec 2014) | 4 lines
scripts/rebuild-rhel-kernel-rpm: Fix an error message
Reported-by: Hiroyuki Sato <hiroysato@gmail.com>
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r5904 | bvassche | 2014-12-03 19:06:57 +0200 (Wed, 03 Dec 2014) | 1 line
iscsi-scst/kernel/patches/rhel/put_page_callback-2.6.32-504.patch: Add
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r5905 | bvassche | 2014-12-03 19:07:31 +0200 (Wed, 03 Dec 2014) | 1 line
scripts/rebuild-rhel-kernel-rpm: Add support for RHEL 6.6
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r5910 | bvassche | 2014-12-04 13:50:58 +0200 (Thu, 04 Dec 2014) | 1 line
scripts/generate-kernel-patch: Swap two filters
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r5912 | bvassche | 2014-12-04 14:19:56 +0200 (Thu, 04 Dec 2014) | 4 lines
/etc/init.d/scst: Exit with status code 0 upon 'start' if already running
Reported-by: Dimitar Tanev <dimitar@linuxdevgroup.org>
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r5913 | vlnb | 2014-12-05 01:41:52 +0200 (Fri, 05 Dec 2014) | 3 lines
FORMAT commands should be strictly serialized
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r5914 | vlnb | 2014-12-05 01:43:51 +0200 (Fri, 05 Dec 2014) | 3 lines
Oops, fix for the previous commit
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r5928 | vlnb | 2014-12-06 07:02:27 +0200 (Sat, 06 Dec 2014) | 3 lines
Web updates
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r5929 | bvassche | 2014-12-09 14:33:16 +0200 (Tue, 09 Dec 2014) | 1 line
rpm build: Add support for qla2x00t driver in QLogic git repository
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r5931 | vlnb | 2014-12-11 06:27:17 +0200 (Thu, 11 Dec 2014) | 3 lines
Docs update
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r5932 | vlnb | 2014-12-11 06:34:36 +0200 (Thu, 11 Dec 2014) | 8 lines
scst_vdisk: Increase virtual device name length
This change makes integration with OpenStack easier since OpenStack GUIDs
are 36 characters long: 32 hex characters and four dashes.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
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r5933 | vlnb | 2014-12-11 06:38:04 +0200 (Thu, 11 Dec 2014) | 11 lines
vdisk_blockio: Report invalid scatterlists
It is possible for a target driver to pass a scatterlist via
scst_cmd_set_tgt_sg() that is valid for the vdisk_fileio handler
but not for the vdisk_blockio handler. Complain loudly if an invalid
scatterlist is passed to vdisk_blockio because such scatterlists
cause silent data corruption with most Linux block drivers.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
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r5934 | bvassche | 2014-12-11 14:31:03 +0200 (Thu, 11 Dec 2014) | 1 line
scst_vdisk: Follow-up for r5932
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r5935 | bvassche | 2014-12-11 14:37:02 +0200 (Thu, 11 Dec 2014) | 1 line
ib_srpt: Log P_Key during login
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r5936 | bvassche | 2014-12-12 11:29:42 +0200 (Fri, 12 Dec 2014) | 1 line
scripts/generate-kernel-patch: Include scst_pg.sgml instead of sgv_cache.sgml
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r5937 | bvassche | 2014-12-12 11:34:55 +0200 (Fri, 12 Dec 2014) | 1 line
doc/scst_pg.sgml: Remove trailing whitespace
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r5938 | bvassche | 2014-12-17 09:48:40 +0200 (Wed, 17 Dec 2014) | 1 line
nightly build: Update kernel versions
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r5939 | vlnb | 2014-12-19 05:50:58 +0200 (Fri, 19 Dec 2014) | 3 lines
Fallback to the old qla driver if the git one not detected
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r5940 | vlnb | 2014-12-19 05:55:14 +0200 (Fri, 19 Dec 2014) | 7 lines
Replace in cases, where sporadic failures are possible, HARDWARE ERROR
by INTERNAL TARGET FAILURE, which is retriable (some OS'es don't retry
HARDWARE ERROR)
Reported and suggested by Shahar Salzman <shahar.salzman@kaminario.com>
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r5941 | vlnb | 2014-12-20 05:48:07 +0200 (Sat, 20 Dec 2014) | 7 lines
scst_vdisk: Only accept NAA IDs allowed by SPC
See also paragraph 7.8.6.6 NAA designator format in SPC-4.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
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r5942 | vlnb | 2014-12-20 05:49:23 +0200 (Sat, 20 Dec 2014) | 11 lines
scst_vdisk: Remove superfluous llseek() calls
vfs_read() and vfs_write() ignore the file offset set by llseek().
Hence remove the llseek() calls that occur just before vfs_read() and
vfs_write(). See also the implementation in the Linux kernel of the
pread64() and pwrite64() system calls for examples of code that uses
vfs_read() and vfs_write().
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
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r5943 | bvassche | 2014-12-22 14:28:13 +0200 (Mon, 22 Dec 2014) | 1 line
Source code spelling fix: Equivilant -> Equivalent
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r5944 | bvassche | 2014-12-22 14:28:56 +0200 (Mon, 22 Dec 2014) | 1 line
Source code spelling fix: accesss -> access
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r5945 | bvassche | 2014-12-22 14:29:51 +0200 (Mon, 22 Dec 2014) | 1 line
Source code spelling fix: addres -> address
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r5946 | bvassche | 2014-12-22 14:31:08 +0200 (Mon, 22 Dec 2014) | 1 line
Source code spelling fix: authentification -> authentication
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r5947 | bvassche | 2014-12-22 14:32:30 +0200 (Mon, 22 Dec 2014) | 1 line
Source code comment spelling fix: explicitely -> explicitly
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r5948 | bvassche | 2014-12-22 14:33:06 +0200 (Mon, 22 Dec 2014) | 1 line
Source code comment spelling fix: hander -> handler
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r5949 | bvassche | 2014-12-22 14:33:37 +0200 (Mon, 22 Dec 2014) | 1 line
Source code comment spelling fix: loosing -> losing
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r5950 | bvassche | 2014-12-22 14:35:00 +0200 (Mon, 22 Dec 2014) | 1 line
Spelling fix: occured -> occurred
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r5951 | bvassche | 2014-12-22 14:35:51 +0200 (Mon, 22 Dec 2014) | 1 line
Source code comment spelling fix: refering -> referring
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r5952 | bvassche | 2014-12-22 14:36:47 +0200 (Mon, 22 Dec 2014) | 1 line
Spelling fix: shrinked -> shrunk
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r5953 | bvassche | 2014-12-22 15:08:34 +0200 (Mon, 22 Dec 2014) | 1 line
Spelling fix: choosen -> chosen
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r5954 | bvassche | 2014-12-22 15:09:20 +0200 (Mon, 22 Dec 2014) | 1 line
Spelling fix: existant -> existent
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r5955 | bvassche | 2014-12-22 15:10:41 +0200 (Mon, 22 Dec 2014) | 1 line
Update for kernel 3.18
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r5956 | bvassche | 2014-12-22 15:15:55 +0200 (Mon, 22 Dec 2014) | 1 line
Spelling fix: immediatelly -> immediately
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r5957 | bvassche | 2014-12-24 16:28:36 +0200 (Wed, 24 Dec 2014) | 1 line
nightly build: Add kernel 3.18
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r5958 | bvassche | 2014-12-29 14:14:52 +0200 (Mon, 29 Dec 2014) | 1 line
scst_lib: Convert spaces into tabs (reported by checkpatch)
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r5959 | bvassche | 2015-01-06 15:25:28 +0200 (Tue, 06 Jan 2015) | 1 line
scst_calc_block_shift: Log block shift and sector size upon mismatch
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r5960 | bvassche | 2015-01-07 11:20:06 +0200 (Wed, 07 Jan 2015) | 4 lines
scst_local: Fix unique per session sas address
Signed-off-by: Sebastian Herbszt <herbszt@gmx.de>
........
r5961 | bvassche | 2015-01-09 14:23:25 +0200 (Fri, 09 Jan 2015) | 4 lines
scst_sysfs: return EINVAL on too big LUN
Signed-off-by: Sebastian Herbszt <herbszt@gmx.de>
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r5962 | bvassche | 2015-01-10 17:52:57 +0200 (Sat, 10 Jan 2015) | 1 line
nightly build: Update kernel versions
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r5963 | bvassche | 2015-01-13 10:42:28 +0200 (Tue, 13 Jan 2015) | 10 lines
scst: Switch to thread context before executing a reservation command
Persistent reservation commands need thread context because
scst_pr_is_cmd_allowed() locks the PR mutex. Reservation commands
either need BH or thread context. Hence switch from atomic to
thread context before processing such commands.
Reported-by: Shahar Salzman <shahar.salzman@kaminario.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
........
r5964 | bvassche | 2015-01-13 10:51:08 +0200 (Tue, 13 Jan 2015) | 5 lines
scst_parse_unmap_descriptors(): Avoid using GFP_KERNEL in atomic context
Reported-by: Shahar Salzman <shahar.salzman@kaminario.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
........
r5965 | bvassche | 2015-01-13 10:55:46 +0200 (Tue, 13 Jan 2015) | 68 lines
qla2x00t: Copy entire SCST sense buffer to q2x ctio
There seems to be a bug in passing sense information to QLA HBAs, where
the last 2 bytes of the sense data (ASC, ASCQ) are not copied to the low
level sense buffer.
We encountered this in ESX, which relies on these 2 bytes to parse the
MISCOMPARE sense code (0xE1, 0x1D, 0x00).
Bellow is a simple test to recreate this issue, but during vMotion
operations (where VMs are moved from one host to another), this may
cause the operation to fail leaving the VM in an inconsistent state.
The test I ran to verify that we are indeed missing the bytes is the
following:
1. Create a SCST based device
2. Expose the device to 2 ESX hosts
3. Format the device as VMFS5, create a test directory
4. From both hosts, I start writing to this directory (no VMs involved,
just write normal files)
At this stage, both ESX hosts try to take access to the directory.
The VMFS filesystem contains a per-directory lock which is managed by
COMPARE AND WRITE command.
Each ESX will attempt to change the VMFS lock location from unlocked to
locked to create the new file.
Obviously there are bound to be failures (which are equivalent to
programming locking conflicts), these are reported by the MISCOMPARE
sense code.
Upon these MISCOMPARE errors, the host will re-try taking the lock until
it succeeds, and will then proceed to perform the write operation on the
directory.
Due to the bug in copying the sense buffer from the SCST core to the QLA
ctio, instead of the full sense code, only the key (0xE) is sent, and
ESX does not know how to handle it resulting in IO error.
Here are the errors as they appear on the command line:
/vmfs/volumes/54a297c4-ca5af1cc-7f94-002219d20f28/ats_test #
./open_close_test-esx2.sh
./open_close_test-esx2.sh: line 8: can't create
ats_fileoptest-esx2_1.txt: Input/output error
./open_close_test-esx2.sh: line 8: can't create
ats_fileoptest-esx2_21.txt: Input/output error
./open_close_test-esx2.sh: line 8: can't create
ats_fileoptest-esx2_110.txt: Input/output error
./open_close_test-esx2.sh: line 8: can't create
ats_fileoptest-esx2_111.txt: Input/output error
In the /var/log/vmkernel.log, we can see that the sense information is
missing (0xE, 0x0, 0x0) instead of (0xE, 0x1D, 0x0).
2014-12-30T12:13:20.714Z cpu6:33519)ScsiDeviceIO: 2338:
Cmd(0x412e84f957c0) 0x89, CmdSN 0x234d from world 519051 to dev
"eui.0024f400d5020007" failed H:0x0 D:0x2 P:0x0 Valid sense data: 0xe 0x0 0x0.
2014-12-30T12:13:20.766Z cpu6:33519)ScsiDeviceIO: 2338:
Cmd(0x412e84f91d00) 0x89, CmdSN 0x2350 from world 519051 to dev
"eui.0024f400d5020007" failed H:0x0 D:0x2 P:0x0 Valid sense data: 0xe 0x0 0x0.
2014-12-30T12:13:20.766Z cpu6:33519)ScsiDeviceIO: 2338:
Cmd(0x412e80449fc0) 0x89, CmdSN 0x234f from world 519051 to dev
"eui.0024f400d5020007" failed H:0x0 D:0x2 P:0x0 Valid sense data: 0xe 0x0 0x0.
This patch fixes this issue, the test will run without a problem with the
fix (no IO errors, all the files are properly written to the directory).
Signed-off-by: Shahar Salzman <shahar.salzman@kaminario.com>
Reviewed-by: Eran Mann <eran.mann@kaminario.com>
[bvanassche: simplified implementation]
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
........
r5966 | bvassche | 2015-01-13 11:38:09 +0200 (Tue, 13 Jan 2015) | 5 lines
qla2x00t: Register for RSCNs in target mode
The QLogic firmware and qla2xxx do not register for RSCNs in
target-only mode, so do that explicitly.
........
r5967 | bvassche | 2015-01-14 10:06:12 +0200 (Wed, 14 Jan 2015) | 1 line
scst_targ: Use tabs instead of spaces for indentation (detected by checkpatch)
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r5968 | bvassche | 2015-01-15 10:58:39 +0200 (Thu, 15 Jan 2015) | 4 lines
scst_targ: Avoid triggering a kernel panic if dev_user_parse() returns SCST_CMD_STATE_STOP
Reported-by: Ilan Steinberg <ilan.steinberg@kaminario.com>
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r5969 | vlnb | 2015-01-16 03:21:10 +0200 (Fri, 16 Jan 2015) | 3 lines
Fix READ BUFFER and WRITE BUFFER commands
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r5970 | vlnb | 2015-01-16 05:16:26 +0200 (Fri, 16 Jan 2015) | 3 lines
Follow up for r5968
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r5971 | vlnb | 2015-01-16 05:53:29 +0200 (Fri, 16 Jan 2015) | 5 lines
Report during user devices unjam LUN NOT SUPPORTED sense
Reported-By: shahar.salzman <shahar.salzman@kaminario.com>
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r5972 | bvassche | 2015-01-16 15:01:58 +0200 (Fri, 16 Jan 2015) | 2 lines
scst.spec.in: Rename variable kver into kversion
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r5973 | bvassche | 2015-01-16 15:12:22 +0200 (Fri, 16 Jan 2015) | 2 lines
scst.spec.in: Pass kernel version via RPM-variable %{kversion} instead of shell variable ${KVER}
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r5974 | bvassche | 2015-01-16 15:16:06 +0200 (Fri, 16 Jan 2015) | 6 lines
scst.spec.in: Determine version number correctly on a koji server
This patch has been tested on a koji build server and also on four
different RPM-based distributions (CentOS 7, Fedora 20, openSuSE 13.2
and SLES 11 SP3).
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r5975 | bvassche | 2015-01-16 18:12:38 +0200 (Fri, 16 Jan 2015) | 1 line
scst.spec.in: Leave out kernel version from RPM name
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r5976 | bvassche | 2015-01-16 18:20:10 +0200 (Fri, 16 Jan 2015) | 1 line
scst.spec.in: Add DKMS support
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r5977 | vlnb | 2015-01-20 06:18:07 +0200 (Tue, 20 Jan 2015) | 3 lines
Revert r5964 as not needed
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r5978 | vlnb | 2015-01-20 06:20:13 +0200 (Tue, 20 Jan 2015) | 3 lines
Revert r5963 as not needed
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r5979 | bvassche | 2015-01-20 17:04:23 +0200 (Tue, 20 Jan 2015) | 13 lines
scst: Rework SCSI pass-through support for kernel versions >= 2.6.30
Changes in this patch:
- Rework the SCSI pass-through code such that for kernel versions
>= 2.6.30 the scst_exec_req_fifo patch is no longer needed.
- Modify the pass-through code such that blk_rq_append_bio() is only
called for kernel version 2.6.30. For later kernel versions
blk_make_request() is called instead.
- Rework scst_scsi_exec_async().
- Add debug tracing of SCSI pass-through result status.
- Add a lockdep_assert_held() call in scsi_end_async().
........
r5980 | bvassche | 2015-01-20 19:13:13 +0200 (Tue, 20 Jan 2015) | 1 line
nightly build: Update kernel versions
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r5981 | vlnb | 2015-01-21 06:15:42 +0200 (Wed, 21 Jan 2015) | 3 lines
Follow up for r5979
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r5982 | vlnb | 2015-01-21 06:20:53 +0200 (Wed, 21 Jan 2015) | 5 lines
Fix returning changeable values for caching mode page
Reported by Consus <consus@gmx.com>
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r5983 | bvassche | 2015-01-21 15:11:56 +0200 (Wed, 21 Jan 2015) | 1 line
scst.h: Fix a sparse warning for kernels 2.6.29..2.6.31
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r5984 | vlnb | 2015-01-22 07:03:17 +0200 (Thu, 22 Jan 2015) | 9 lines
[PATCH] scst_local: Fix bidirectional command support
scsi_setup_cmnd() sets sc_data_direction to DMA_TO_DEVICE for bidirectional
commands. Hence test SCpnt->request->next_rq instead of sc_data_direction
to figure out whether or not a command is bidirectional.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
........
r5985 | vlnb | 2015-01-22 07:06:45 +0200 (Thu, 22 Jan 2015) | 12 lines
[PATCH] scst_main: Suppress a checkpatch warning triggered by INIT_CACHEP{,_ALIGN}
Avoid that checkpatch v3.18 reports the following warning for these
two macros:
WARNING: Macros with flow control statements should be avoided
This patch does not change any functionality.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
........
r5986 | vlnb | 2015-01-22 07:09:17 +0200 (Thu, 22 Jan 2015) | 9 lines
scst_vdisk: Micro-optimize vdisk_caching_pg
This patch does not change any behavior but micro-optimizes
vdisk_caching_pg(). Declaring the array caching_pg[] const reduces
11 bytes from the assembler code of this function.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
........
r5987 | vlnb | 2015-01-22 07:10:42 +0200 (Thu, 22 Jan 2015) | 10 lines
scst: Suppress a smatch warning in vdisk_unmap_range()
Avoid that the static source code analysis tool 'smatch' reports
the following warning:
vdisk_unmap_range() warn: should 'blocks << cmd->dev->block_shift' be a 64 bit type?
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
........
r5988 | vlnb | 2015-01-22 07:13:59 +0200 (Thu, 22 Jan 2015) | 27 lines
scst_vdisk: Fix zero-copy read for tmpfs
For some filesystems, e.g. tmpfs, address_space.readpage is NULL.
Disable zero-copy reading for such filesystems. See also shmem_aops
in mm/shmem.c. See also inode_init_always() and empty_aops in fs/inode.c.
This patch avoids that the following call trace is triggered:
BUG: unable to handle kernel NULL pointer dereference at (null)
Call Trace:
[<ffffffffa0547d66>] prepare_read+0x106/0x1d0 [scst_vdisk]
[<ffffffffa0547f20>] fileio_alloc_data_buf+0xf0/0x330 [scst_vdisk]
[<ffffffffa046fc9b>] scst_prepare_space+0x9b/0x6e0 [scst]
[<ffffffffa047d4d5>] scst_process_active_cmd+0x545/0x840 [scst]
[<ffffffffa047dad2>] scst_cmd_init_done+0x302/0x5d0 [scst]
[<ffffffffa0563ab2>] scst_cmd_init_stage1_done.constprop.37+0x12/0x20 [iscsi_scst]
[<ffffffffa056a9ea>] scsi_cmnd_start+0x25a/0x550 [iscsi_scst]
[<ffffffffa056b4a8>] cmnd_rx_start+0x148/0x1a0 [iscsi_scst]
[<ffffffffa056e4f8>] process_read_io+0x3b8/0x800 [iscsi_scst]
[<ffffffffa056ea07>] scst_do_job_rd+0xc7/0x220 [iscsi_scst]
[<ffffffffa056efed>] istrd+0x16d/0x2e0 [iscsi_scst]
[<ffffffff81079efd>] kthread+0xed/0x110
[<ffffffff817227fc>] ret_from_fork+0x7c/0xb0
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
........
r5989 | vlnb | 2015-01-24 07:37:57 +0200 (Sat, 24 Jan 2015) | 5 lines
scst_local: Rework data direction detection code
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
........
r5990 | bvassche | 2015-01-26 13:32:32 +0200 (Mon, 26 Jan 2015) | 1 line
ib_srpt: Detect Mellanox OFED 2.3 correctly
........
r5991 | vlnb | 2015-01-28 07:07:46 +0200 (Wed, 28 Jan 2015) | 3 lines
Cleanups
........
git-svn-id: http://svn.code.sf.net/p/scst/svn/branches/iser@5993 d57e44dd-8a1f-0410-8b47-8ef2f437770f
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<li><a href="downloads.html">Downloads</a></li>
|
|
<li><a href="contributing.html">Contributing</a></li>
|
|
<li id="current"><a href="comparison.html">Comparison</a></li>
|
|
<li><a href="users.html">Users</a></li>
|
|
<li><a href="solutions.html">Solutions</a></li>
|
|
</ul>
|
|
</div>
|
|
|
|
<!-- content-wrap starts here -->
|
|
<div id="content-wrap">
|
|
<div id="sidebar">
|
|
<h1>Comparison</h1>
|
|
<ul class="sidemenu">
|
|
<li><a href="comparison.html">Features comparison</a></li>
|
|
<li><a href="scstvslio.html">SCST vs LIO/TCM</a></li>
|
|
<li><a href="scstvsstgt.html">SCST vs STGT</a></li>
|
|
<li><a href="mc_s.html">MC/S vs MPIO</a></li>
|
|
</ul>
|
|
</div>
|
|
|
|
<div id="main">
|
|
<h1>Features comparison between Linux SCSI targets</h1>
|
|
|
|
<p>This features comparison is intended to be a complete and fair feature-by-feature
|
|
comparison between the listed targets without any bias to SCST. If you see anything
|
|
wrong somewhere or anything missed, you are welcome to report it in scst-devel
|
|
mailing list and it will be corrected.
|
|
</p>
|
|
|
|
<p>Also Sebastian Riemer wrote a good summary in <a href="http://sourceforge.net/mailarchive/message.php?msg_id=30688206" rel="nofollow">his e-mail</a> (April 2013)</p>
|
|
|
|
<p><small>As on June 2011, briefly reviewed April 2013.</small></p>
|
|
|
|
<table bgcolor="#F0F0F0" border="1" cellspacing="1" cellpadding="7" style="text-align:center" width="620">
|
|
|
|
<tr>
|
|
<td>
|
|
</td><td><b><a href="http://scst.sourceforge.net/" title="http://scst.sourceforge.net/" rel="nofollow">SCST</a></b>
|
|
</td><td><b><a href="http://stgt.berlios.de/" title="http://stgt.berlios.de/" rel="nofollow">STGT</a></b>
|
|
</td><td><b><a href="http://iscsitarget.sourceforge.net/" title="http://iscsitarget.sourceforge.net/" rel="nofollow">IET</a></b>
|
|
</td><td><b><a href="scstvslio.html">LIO/TCM</a></b>
|
|
</td></tr>
|
|
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>General</b>
|
|
</td></tr>
|
|
<tr>
|
|
<td align="left"><b>Upstream kernel</b></td> <td> - </td> <td> - </td> <td> - </td> <td> <a href="scstvslio.html">Since 2.6.38</a></td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Generic Target Engine</b></td> <td> + </td> <td> + </td> <td> iSCSI only </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Architecture</b></td> <td> Kernel only</td> <td> User space only </td> <td> Split <sup>
|
|
<A HREF="#1">1</A>
|
|
</sup> </td> <td> Kernel only </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Stability</b></td> <td> + </td> <td> + </td> <td> + </td> <td> Probably </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Performance <sup><A HREF="#2">2</A></sup></b></td> <td> ***** <sup>
|
|
<A HREF="#3">3</A>
|
|
</sup></td> <td> ***</td> <td> **** </td> <td> ****- </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Zero-copy passing data between target and
|
|
backend drivers</th> <td> + <sup>
|
|
<A HREF="#4">4</A>
|
|
</sup></td> <td> + <sup>
|
|
<A HREF="#5">5</A>
|
|
</sup> </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Support for transports without expecting
|
|
transfer values (Wide (parallel) SCSI, SAS)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Interface with user space</b></td> <td> SysFS (or obsolete
|
|
ProcFS)</td> <td> Custom </td> <td> - </td> <td> ConfigFS/IOCTL/ProcFS </td>
|
|
</tr>
|
|
|
|
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"><b>Features</b>
|
|
</td></tr>
|
|
<tr>
|
|
<td align="left"><b>Target drivers in kernel space</b></td> <td> + </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Target drivers in user space</b></td> <td>Via scst_local (e.g.
|
|
using STGT
|
|
pass-through)</td> <td> + </td> <td> - </td> <td>Via tcm_loop (e.g.
|
|
using STGT pass-through)</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Backstorage handlers in kernel space</b></td> <td> + </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Backstorage handlers in user space</b></td> <td>+</td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Advanced devices access control
|
|
<sup><A HREF="#7">7</A></sup></b></td> <td> + </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Automatic sessions reassignment (changes in the
|
|
access control immediately seen by initiators)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Support for Asynchronous Event Notifications
|
|
(AEN)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Notifications for devices added/removed or
|
|
resized through AENs or Unit Attentions (initiators can instantly see
|
|
any target reconfiguration in a PnP-like manner)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Bidirectional Commands</b></td> <td> +</td> <td> + </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Extended CDB (size >16 bytes)</b></td> <td> +</td> <td> + </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Descriptor sense support</b></td> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>RESERVE/RELEASE
|
|
(Windows 2003 clustering)</b></td> <td> + </td> <td> + </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Safe RESERVE/RELEASE implementation according to
|
|
SCSI requirements <sup><A HREF="#9">9</A></sup></b></td> <td> Safe </td> <td> Safe </td> <td> Safe from
|
|
v1.4.18</td> <td> Not safe </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Safe implementation of Task Management commands
|
|
<sup><A HREF="#10">10</A></sup></b></td> <td> Safe </td> <td> Not safe </td> <td> Not safe </td> <td> LUN RESET - safe.
|
|
Other TM commands not
|
|
implemented. </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Support for SCSI task attributes, including
|
|
ORDERED commands</b></td> <td> + </td> <td> + </td> <td> -, <br> data
|
|
corruption possible
|
|
<sup><A HREF="#11">
|
|
11</A></sup></td> <td> -, <br>data
|
|
corruption possible
|
|
<sup><A HREF="#11">
|
|
11</A></sup> </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Persistent (SCSI-3) Reservations
|
|
(Windows 2008 clustering / RHEL5 I/O fencing)</b></td> <td> + </td> <td> + <br> (not all
|
|
functionality
|
|
implemented)</td> <td> - </td> <td> + </td>
|
|
<tr>
|
|
<td align="left"><b>Durable, i.e. transactional, save of Persistent
|
|
Through Power Loss Persistent Reservation data</b></td> <td> Durable </td> <td>Not supported</td> <td> - </td> <td> Not durable </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>ALUA</b></td> <td> +/- (Implicit
|
|
only)<sup>
|
|
<A HREF="#19">19</A>
|
|
</sup> </td> <td> - </td> <td> - </td> <td> +/-<sup><A HREF="#19">
|
|
19</A></sup></td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Failover Clustering</b></td> <td> + </td> <td> + </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Different threading models to choose the best
|
|
performing</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>CPU affinity control</b></td> <td> + </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>I/O context grouping between I/O threads (big
|
|
performance win with CFQ)</b></td> <td> + </td> <td> - </td> <td> + </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Per-initiator I/O context grouping (big
|
|
performance and fairness win if several initiators access the same
|
|
virtual or backend device on the target)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Protection against commands with
|
|
wrong transfer size or transfer direction (may lead to crash or
|
|
hard lockup of the target)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Protection against crashing target by making it
|
|
to allocate too much memory for buffers and go into OOM state
|
|
</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Caching of allocated buffers</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Latencies measurement facility</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Configuration tool with ability to automatically
|
|
apply changes in the config file on fly without any restarts</b></td> <td> scstadmin </td> <td> - </td> <td> - </td> <td> rtsadmin? </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>SCSI MIBs</b></td> <td> - </td> <td> - </td> <td> - </td> <td> +-
|
|
<sup><A HREF="#12">12</A></sup></td>
|
|
</tr>
|
|
|
|
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>Supported transports and hardware</b>
|
|
</td></tr>
|
|
<tr>
|
|
<td align="left"><b>iSCSI</b></td> <td> + </td> <td> + </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>QLogic (Fibre Channel and FCoE)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> +</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Emulex (Fibre Channel and FCoE)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>SRP</b></td> <td> + </td> <td> - </td> <td> - </td> <td> Preliminary </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>iSER</b></td> <td> + </td> <td> + </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Marvell (SAS)</b></td> <td> Beta </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>FCoE</b></td> <td> + </td> <td>Under
|
|
development</td> <td> - </td> <td> Alpha </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>LSI (Parallel (Wide) SCSI and Fibre Channel)
|
|
</b></td> <td> Alpha </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>LSI (SAS)</b></td> <td> Preliminary
|
|
(not completed) </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>IBM pSeries Virtual SCSI</b></td> <td> + </td> <td> + </td> <td> - </td> <td> Preliminary </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Local access to emulated backstorage devices
|
|
<sup><A HREF="#6">6</A></sup></b></td> <td> scst_local </td> <td> - </td> <td> - </td> <td> tcm_loop </td>
|
|
</tr>
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>Supported backstorage</b>
|
|
</td></tr>
|
|
<tr>
|
|
<td align="left"><b>Kernel side FILEIO</b></td> <td> + </td> <td> - </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Kernel side BLOCKIO</b></td> <td> + </td> <td> - </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>User space FILEIO</b></td> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>O_DIRECT FILEIO</b></td> <td> fileio_tgt </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Async FILEIO</b></td> <td> - </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Native RAMDISK</b></td> <td> - </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>SCSI pass-through
|
|
<sup><A HREF="#13">13</A></sup></b></td> <td> + </td> <td> Single
|
|
initiator only, not
|
|
enforced<sup>
|
|
<A HREF="#14">14</A>
|
|
</sup> </td> <td> - </td> <td> Single initiator only, not enforced,
|
|
limited functionality for tapes
|
|
<sup><A HREF="#14">14</A></sup></td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Zero-copy data read/write to/from backstorage
|
|
</b></td> <td>BLOCKIO, user space
|
|
FILEIO in O_DIRECT mode,
|
|
pass-through <sup>
|
|
<A HREF="#15">15</A>
|
|
</sup></td> <td> - <sup>
|
|
<A HREF="#5">5</A>
|
|
</sup> </td> <td> BLOCKIO </td> <td> BLOCKIO, pass-
|
|
through </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Cache safe<sup><A HREF="#8">8</A></sup>
|
|
FILEIO</b></td> <td> Safe </td> <td>Safe only RDWR
|
|
backend</td> <td> Safe </td> <td> Safe </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Cache safe<sup><A HREF="#8">8</A></sup>
|
|
BLOCKIO</b></td> <td> Safe </td> <td> - </td> <td> Not safe </td> <td> Safe </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>4k sectors support in pass-through mode</b></td> <td> + </td> <td> - </td> <td> - </td> <td> ? </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>4k, 2k, 1k and 512 byte sectors emulation
|
|
in modes, other than pass-through</b></td> <td> + </td> <td> + </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Virtual CD devices emulation from ISO files
|
|
</b></td> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Possibility to write to emulated from ISO files
|
|
CD devices</b></td> <td> - </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Emulation of virtual tape and media changer
|
|
devices (VTL)</b></td> <td> - </td> <td>Experimental</td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Thin provisioning support</b></td> <td>+<br></td> <td> ? </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>iSCSI Target</b>
|
|
</td></tr>
|
|
<tr>
|
|
<td align="left"><b>Architecture</b></td> <td> Split <sup>
|
|
<A HREF="#1">1</A>
|
|
</sup> </td> <td> User space
|
|
only </td> <td> Split <sup>
|
|
<A HREF="#1">1</A>
|
|
</sup></td> <td> Kernel only </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Interface with user space</b></td> <td>SysFS (or obsolete
|
|
ProcFS)/
|
|
IOCTL/Netlink</td> <td> - </td> <td>IOCTL/ProcFS/
|
|
Netlink</td> <td> ConfigFS/IOCTL/ProcFS </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Zero-copy data send/receive</b></td> <td> Send only<sup>
|
|
<A HREF="#16">16</A>
|
|
</sup> </td> <td> In some cases,
|
|
send only <sup>
|
|
<A HREF="#5">5</A>
|
|
</sup> </td> <td> Send only</td> <td> Send only </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b><a href="mc_s.html">Multiple connections per
|
|
session (MS/C)</a></b></td> <td> - </td> <td> - </td> <td>+</td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Max ErrorRecoveryLevel</b></td> <td> 0 </td> <td> 0 </td> <td> 0 </td> <td> 2 </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Support for limiting number of initiators
|
|
allowed to connect to a target</b></td> <td> + </td> <td> - </td> <td> + </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Per-portal targets visibility control</b></td> <td> + </td> <td> - </td> <td> + </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Per-initiators targets visibility control</b></td> <td> + </td> <td> + </td> <td> + </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Support for AHS</b></td> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Support for iSCSI redirects</b></td> <td> + </td> <td> + </td> <td> + </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Bidirectional Commands</b></td> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Extended CDB (size >16 bytes)</b></td> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Support for AENs (initiators can instantly see any
|
|
target reconfiguration in a PnP-like manner)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Support for iSNS</b></td> <td> + </td> <td> + </td> <td> + </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Safe implementation of Task Management commands
|
|
<sup><A HREF="#10">10</A></sup></b></td> <td> Safe </td> <td> Not safe </td> <td> Not safe </td> <td> ABORT TASK - not safe,
|
|
LUN RESET - safe,
|
|
other TM commands not
|
|
implemented. </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Safe implementation of connections and sessions
|
|
reinstatement <sup><A HREF="#17">17</A></sup></b></td> <td> Safe </td> <td> Not safe </td> <td> Not safe </td> <td> Not safe </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Usage of hardware instructions for digest
|
|
calculations, if available</b></td> <td> + </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Each connection multithreaded digest calculation
|
|
</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Safe restart <sup><A HREF="#18">18</A></sup>
|
|
</b></td> <td> Safe </td> <td> ? </td> <td> Not safe before
|
|
v1.4.18. After -
|
|
probably safe.</td> <td> ?</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>iSCSI MIBs</b></td> <td> - </td> <td> - </td> <td> - </td> <td> +-
|
|
<sup><A HREF="#12">12</A></sup></td>
|
|
</tr>
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>Local access target</b>
|
|
</td></tr>
|
|
<tr>
|
|
<td align="left"><b>Bidirectional support</b></td> <td> + </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<td align="left"><b>Support for AENs (initiators can instantly see any
|
|
target reconfiguration in a PnP-like manner)</b></td> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
</table>
|
|
|
|
<br>
|
|
<p><strong><big><u>REMARKS:</u></big></strong></p>
|
|
|
|
<p><A NAME="1"></A> 1. All iSCSI management implemented in user space and actual data transfers in kernel space without user space involved.</p>
|
|
|
|
<p><A NAME="2"></A> 2. The result "in average" is listed. One target can be better somewhere, another one somewhere else. Although manual tuning of target and
|
|
system parameters tends the restore the difference listed in the comparison. You can find example measurements <a href="vl_res.txt">here</a>,
|
|
<a href="bart_res.txt">here</a> and <a href="tomasz_res.txt">here</a>.</p>
|
|
|
|
<p><A NAME="3"></A> 3. All SCST and its drivers' kernel patches supposed to be applied and SCST with the drivers built in the release or performance build.
|
|
Without the kernel patches SCST performance will be at "****+" level, except for the case, when user space backstorage handler used
|
|
with iSCSI-SCST iSCSI target driver, where performance will be at "***+" level.</p>
|
|
|
|
<p><A NAME="4"></A> 4 In SCST data are always passed in zero-copy manner between target and backend drivers without need for any
|
|
additional kernel patches, except in case, when local access (scst_local) used with user space backend. </p>
|
|
|
|
<p><A NAME="5"></A> 5. Some zero-copy functionality isn't available from user space, sometimes fundamentally.
|
|
For instance, zero-copy FILEIO with page cache or zero-copy send to a socket. Also STGT can't use splice() for in-kernel
|
|
target drivers, because it has memory management in user space. To use splice() with socket-based user space target drivers
|
|
STGT would need a deep redesign of internal interactions between target drivers, core and backend handlers. But in
|
|
some cases STGT can use zero-copy sendfile().</p>
|
|
|
|
<p><A NAME="6"></A> 6. "Local access to emulated backstorage devices" means that you can access emulated by a SCSI target devices
|
|
locally on the target host. For instance, you can mount your ISO image from emulated by the target
|
|
CDROM device locally on the target host.</p>
|
|
|
|
<p><A NAME="7"></A> 7. "Advanced devices access control" means that different initiators can see different sets
|
|
of devices from the same target. This feature is required for hardware targets, which don't have ability
|
|
to create virtual targets.</p>
|
|
|
|
<p><A NAME="8"></A> 8. "Cache safe" means that cache synchronization commands (SYNCHRONIZE_CACHE and FUA attribute) from initiators perform
|
|
what they expected to perform, i.e. push all the requested blocks from all caches, including devices' caches,
|
|
to non-volatile media.</p>
|
|
|
|
<p><A NAME="9"></A> 9. SCSI requires that if an initiator clears reservation held by another initiator, the reservation holder must be notified
|
|
about the reservation clearance. Otherwise, several initiators can at the same time change supposed to be protected by the
|
|
reservation data, which can corrupt them. This is what was called
|
|
<a href="http://communities.vmware.com/thread/53797?tstart=0&start=15">"Russian roulette with your data"</a> on the VMware
|
|
community forum by someone working for VMware. But, sure, it can affect not only VMware, but also any other cluster
|
|
implementation, relying on this functionality.</p>
|
|
|
|
<p><A NAME="10"></A> 10. After a task management command completed and before the corresponding response was sent to the initiator, who sent that task management
|
|
command, all the affected SCSI commands must get into a state, where they can't affect following after
|
|
the tasks management response commands from this initiator. This is the safe implementation.
|
|
The unsafe implementation only marks all the affected
|
|
SCSI commands as aborted and then immediately send task management response to the initiator. This implementation only
|
|
guarantees that the initiator will never receive responses from those commands, but it doesn't
|
|
guarantee that none of those commands will get executed by backstorage <strong>*AFTER*</strong> any
|
|
SCSI command, which initiator will send after it received the task management response thinking
|
|
that all the aborted commands actually fully aborted. This could lead to a data corruption.</p>
|
|
|
|
<p><A NAME="11"></A> 11. Both IET and LIO report in INQUIRY command response support for full task management model. But they process ORDERED
|
|
commands the same way as SIMPLE commands, i.e. allow free reorder of them before they get executed. That violates SCSI standard
|
|
and can lead to a data corruption to any application relying on commands order provided by ORDERED attribute.</p>
|
|
|
|
<p><A NAME="12"></A> 12. LIO exports the information needed for an RFC 4455 implementation, but requires additional RFC 4455 implementing module.
|
|
At the moment, there is no open source implementation of such module.</p>
|
|
|
|
<p><A NAME="13"></A> 13. SCSI pass-through mode allows to export your local SCSI-capable device. For instance with it you can share your parallel
|
|
SCSI tape or SATA DVD-RW device to your iSCSI network.</p>
|
|
|
|
<p><A NAME="14"></A> 14. STGT and LIO don't emulate all the necessary SCSI host functionality to allow to share SCSI devices
|
|
in pass-through mode to several initiators, although LIO has some necessary processing, but not all.
|
|
They can only pass SCSI commands from initiators to
|
|
SCSI devices and responses back. This is safe only with a single initiator. This limitation
|
|
isn't enforced anyhow and both STGT and LIO don't issue any warning about it, so an user will not be notified about this
|
|
limitation and can quietly corrupt his/her data. You can find more technical information about it
|
|
<a href="http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg06911.html">here</a>.
|
|
Also LIO in pass-through mode doesn't do necessary sense processing for tape devices to
|
|
correctly return residual information, so tapes can used with it with limited functionality.</p>
|
|
|
|
<p><A NAME="15"></A> 15. You can find a proposal how to implement zero-copy FILEIO in SCST on the <a href="contributing.html#ZC_READ">
|
|
Contributing</a> page.</p>
|
|
|
|
<p><A NAME="16"></A> 16. Doesn't need any kernel patch, except in the case, when used with user space backend.</p>
|
|
|
|
<p><A NAME="17"></A> 17. Connections and sessions reinstatement is, basically, a kind of Task Management command, because it implies commands aborting.
|
|
So, similarly to the safe task management above, a safe implementation of connections and sessions reinstatement
|
|
must not accept SCSI commands from new connection/session until all the SCSI commands in
|
|
being reinstated connection/session get into a state, where they can't affect new commands.</p>
|
|
|
|
<p><A NAME="18"></A> 18. "Safe restart" means that after the iSCSI target restart, all the connected initiators will seamlessly restore all existing before
|
|
the restart connections. "Not safe" means that, most likely, the connected initiators will fail to restore
|
|
existing connections with some errors. However, your iSCSI initiator also should be able to handle the safe restart. For instance,
|
|
old (pre-CentOS/RHEL 5) open-iscsi has problems in this area. But the latest versions do it pretty well.</p>
|
|
|
|
<p><A NAME="19"></A> 19. Generic implementation, i.e. not coupled to any particular cluster implementation, which means it is needed additional effort
|
|
to used with each particular cluster setup.</p>
|
|
|
|
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|
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