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Improve zfs-module-parameters(5)

Browse Source 
Various rewrites to the descriptions of module parameters. Corrects
spelling mistakes, makes descriptions them more user-friendly and
describes some ZFS quirks which should be understood before changing
parameter values.

Signed-off-by: DHE <git@dehacked.net>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4671
This commit is contained in:
DHE 2015-12-30 12:44:46 -05:00 committed by Brian Behlendorf
parent cbecb4fb22
commit 8342673502
3 changed files with 97 additions and 55 deletions
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148
man/man5/zfs-module-parameters.5
View File

@ -30,7 +30,8 @@ Description of the different parameters to the ZFS module.
\fBl2arc_feed_again\fR (int)
.ad
.RS 12n
Turbo L2ARC warmup
Turbo L2ARC warm-up. When the L2ARC is cold the fill interval will be set as
fast as possible.
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
@ -41,7 +42,8 @@ Use \fB1\fR for yes (default) and \fB0\fR to disable.
\fBl2arc_feed_min_ms\fR (ulong)
.ad
.RS 12n
Min feed interval in milliseconds
Min feed interval in milliseconds. Requires \fBl2arc_feed_again=1\fR and only
applicable in related situations.
.sp
Default value: \fB200\fR.
.RE
@ -63,7 +65,8 @@ Default value: \fB1\fR.
\fBl2arc_headroom\fR (ulong)
.ad
.RS 12n
Number of max device writes to precache
How far through the ARC lists to search for L2ARC cacheable content, expressed
as a multiplier of \fBl2arc_write_max\fR
.sp
Default value: \fB2\fR.
.RE
@ -74,7 +77,8 @@ Default value: \fB2\fR.
\fBl2arc_headroom_boost\fR (ulong)
.ad
.RS 12n
Compressed l2arc_headroom multiplier
Scales \fBl2arc_headroom\fR by this percentage when L2ARC contents are being
successfully compressed before writing. A value of 100 disables this feature.
.sp
Default value: \fB200\fR.
.RE
@ -110,7 +114,8 @@ Use \fB1\fR for yes and \fB0\fR for no (default).
\fBl2arc_noprefetch\fR (int)
.ad
.RS 12n
Skip caching prefetched buffers
Do not write buffers to L2ARC if they were prefetched but not used by
applications
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
@ -132,7 +137,8 @@ Use \fB1\fR for yes and \fB0\fR for no (default).
\fBl2arc_write_boost\fR (ulong)
.ad
.RS 12n
Extra write bytes during device warmup
Cold L2ARC devices will have \fBl2arc_write_nax\fR increased by this amount
while they remain cold.
.sp
Default value: \fB8,388,608\fR.
.RE
@ -266,7 +272,7 @@ configuration. Pool administrators who understand the factors involved
may wish to specify a more realistic inflation factor, particularly if
they operate close to quota or capacity limits.
.sp
Default value: 24
Default value: \fB24\fR.
.RE
.sp
@ -283,7 +289,7 @@ blocks in the pool for verification. If this parameter is set to 0,
the traversal skips non-metadata blocks. It can be toggled once the
import has started to stop or start the traversal of non-metadata blocks.
.sp
Default value: 1
Default value: \fB1\fR.
.RE
.sp
@ -300,7 +306,7 @@ blocks in the pool for verification. If this parameter is set to 0,
the traversal is not performed. It can be toggled once the import has
started to stop or start the traversal.
.sp
Default value: 1
Default value: \fB1\fR.
.RE
.sp
@ -312,7 +318,7 @@ Default value: 1
Maximum concurrent I/Os during the traversal performed during an "extreme
rewind" (\fB-X\fR) pool import.
.sp
Default value: 10000
Default value: \fB10000\fR.
.RE
.sp
@ -328,7 +334,7 @@ It also limits the worst-case time to allocate space. If we have
less than this amount of free space, most ZPL operations (e.g. write,
create) will return ENOSPC.
.sp
Default value: 5
Default value: \fB5\fR.
.RE
.sp
@ -410,7 +416,8 @@ Default value: \fB10\fR.
\fBzfs_arc_grow_retry\fR (int)
.ad
.RS 12n
Seconds before growing arc size
After a memory pressure event the ARC will wait this many seconds before trying
to resume growth
.sp
Default value: \fB5\fR.
.RE
@ -433,7 +440,12 @@ Default value: \fB10\fR.
\fBzfs_arc_max\fR (ulong)
.ad
.RS 12n
Max arc size
Max arc size of ARC in bytes. If set to 0 then it will consume 1/2 of system
RAM. This value must be at least 67108864 (64 megabytes).
.sp
This value can be changed dynamically with some caveats. It cannot be set back
to 0 while running and reducing it below the current ARC size will not cause
the ARC to shrink without memory pressure to induce shrinking.
.sp
Default value: \fB0\fR.
.RE
@ -450,6 +462,9 @@ be reclaimed even if the overall arc_c_max has not been reached. This
value defaults to 0 which indicates that 3/4 of the ARC may be used
for meta data.
.sp
This value my be changed dynamically except that it cannot be set back to 0
for 3/4 of the ARC; it must be set to an explicit value.
.sp
Default value: \fB0\fR.
.RE
@ -513,9 +528,10 @@ Default value: \fB100\fR.
\fBzfs_arc_min_prefetch_lifespan\fR (int)
.ad
.RS 12n
Min life of prefetch block
Minimum time prefetched blocks are locked in the ARC, specified in jiffies.
A value of 0 will default to 1 second.
.sp
Default value: \fB100\fR.
Default value: \fB0\fR.
.RE
.sp
@ -529,7 +545,7 @@ of lists for both data and meta data objects. Locking is performed at
the level of these "sub-lists". This parameters controls the number of
sub-lists per ARC state.
.sp
Default value: 1 or the number of on-online CPUs, whichever is greater
Default value: \fR1\fB or the number of online CPUs, whichever is greater
.RE
.sp
@ -652,7 +668,8 @@ Default value: \fB4M\fR.
\fBzfs_dbuf_state_index\fR (int)
.ad
.RS 12n
Calculate arc header index
This feature is currently unused. It is normally used for controlling what
reporting is available under /proc/spl/kstat/zfs.
.sp
Default value: \fB0\fR.
.RE
@ -663,7 +680,7 @@ Default value: \fB0\fR.
\fBzfs_deadman_enabled\fR (int)
.ad
.RS 12n
Enable deadman timer
Enable deadman timer. See description below.
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
@ -785,7 +802,7 @@ time, and will be ignored if \fBzfs_dirty_data_max\fR is later changed.
The parameter \fBzfs_dirty_data_max_max\fR takes precedence over this
one. See the section "ZFS TRANSACTION DELAY".
.sp
Default value: 25
Default value: \fN25\fR.
.RE
.sp
@ -841,7 +858,7 @@ Default value: \fB100,000\fR.
\fBzfs_vdev_async_read_max_active\fR (int)
.ad
.RS 12n
Maxium asynchronous read I/Os active to each device.
Maximum asynchronous read I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB3\fR.
@ -895,7 +912,7 @@ Default value: \fB30\fR.
\fBzfs_vdev_async_write_max_active\fR (int)
.ad
.RS 12n
Maxium asynchronous write I/Os active to each device.
Maximum asynchronous write I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
@ -932,7 +949,7 @@ Default value: \fB1,000\fR.
\fBzfs_vdev_scrub_max_active\fR (int)
.ad
.RS 12n
Maxium scrub I/Os active to each device.
Maximum scrub I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB2\fR.
@ -956,7 +973,7 @@ Default value: \fB1\fR.
\fBzfs_vdev_sync_read_max_active\fR (int)
.ad
.RS 12n
Maxium synchronous read I/Os active to each device.
Maximum synchronous read I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
@ -980,7 +997,7 @@ Default value: \fB10\fR.
\fBzfs_vdev_sync_write_max_active\fR (int)
.ad
.RS 12n
Maxium synchronous write I/Os active to each device.
Maximum synchronous write I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
@ -1125,7 +1142,8 @@ Default value: \fB0\fR.
\fBzfs_free_min_time_ms\fR (int)
.ad
.RS 12n
Min millisecs to free per txg
During a \fRzfs destroy\fB operation using \fRfeature@async_destroy\fB a minimum
of this much time will be spent working on freeing blocks per txg.
.sp
Default value: \fB1,000\fR.
.RE
@ -1136,7 +1154,8 @@ Default value: \fB1,000\fR.
\fBzfs_immediate_write_sz\fR (long)
.ad
.RS 12n
Largest data block to write to zil
Largest data block to write to zil. Larger blocks will be treated as if the
dataset being written to had the property setting \fRlogbias=throughput\fB.
.sp
Default value: \fB32,768\fR.
.RE
@ -1191,7 +1210,7 @@ Default value: \fB70\fR.
.ad
.RS 12n
Metaslab groups are considered eligible for allocations if their
fragmenation metric (measured as a percentage) is less than or equal to
fragmentation metric (measured as a percentage) is less than or equal to
this value. If a metaslab group exceeds this threshold then it will be
skipped unless all metaslab groups within the metaslab class have also
crossed this threshold.
@ -1231,7 +1250,8 @@ Default value: \fB0\fR.
\fBzfs_no_scrub_io\fR (int)
.ad
.RS 12n
Set for no scrub I/O
Set for no scrub I/O. This results in scrubs not actually scrubbing data and
simply doing a metadata crawl of the pool instead.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
@ -1242,7 +1262,7 @@ Use \fB1\fR for yes and \fB0\fR for no (default).
\fBzfs_no_scrub_prefetch\fR (int)
.ad
.RS 12n
Set for no scrub prefetching
Set to disable block prefetching for scrubs.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
@ -1253,7 +1273,8 @@ Use \fB1\fR for yes and \fB0\fR for no (default).
\fBzfs_nocacheflush\fR (int)
.ad
.RS 12n
Disable cache flushes
Disable cache flush operations on disks when writing. Beware, this may cause
corruption if disks re-order writes.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
@ -1275,7 +1296,8 @@ Use \fB1\fR for yes (default) and \fB0\fR to disable.
\fBzfs_pd_bytes_max\fR (int)
.ad
.RS 12n
The number of bytes which should be prefetched.
The number of bytes which should be prefetched during a pool traversal
(eg: \fRzfs send\fB or other data crawling operations)
.sp
Default value: \fB52,428,800\fR.
.RE
@ -1311,9 +1333,10 @@ Default value: \fB1,048,576\fR.
\fBzfs_read_history\fR (int)
.ad
.RS 12n
Historic statistics for the last N reads
Historic statistics for the last N reads will be available in
\fR/proc/spl/kstat/zfs/POOLNAME/reads\fB
.sp
Default value: \fB0\fR.
Default value: \fB0\fR (no data is kept).
.RE
.sp
@ -1358,7 +1381,8 @@ Default value: \fB2\fR.
\fBzfs_resilver_min_time_ms\fR (int)
.ad
.RS 12n
Min millisecs to resilver per txg
Resilvers are processed by the sync thread. While resilvering it will spend
at least this much time working on a resilver between txg flushes.
.sp
Default value: \fB3,000\fR.
.RE
@ -1383,7 +1407,8 @@ Default value: \fB50\fR.
\fBzfs_scan_min_time_ms\fR (int)
.ad
.RS 12n
Min millisecs to scrub per txg
Scrubs are processed by the sync thread. While scrubbing it will spend
at least this much time working on a scrub between txg flushes.
.sp
Default value: \fB1,000\fR.
.RE
@ -1407,7 +1432,7 @@ Default value: \fB4\fR.
\fBzfs_send_corrupt_data\fR (int)
.ad
.RS 12n
Allow to send corrupt data (ignore read/checksum errors when sending data)
Allow sending of corrupt data (ignore read/checksum errors when sending data)
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
@ -1418,7 +1443,7 @@ Use \fB1\fR for yes and \fB0\fR for no (default).
\fBzfs_sync_pass_deferred_free\fR (int)
.ad
.RS 12n
Defer frees starting in this pass
Flushing of data to disk is done in passes. Defer frees starting in this pass
.sp
Default value: \fB2\fR.
.RE
@ -1440,7 +1465,7 @@ Default value: \fB5\fR.
\fBzfs_sync_pass_rewrite\fR (int)
.ad
.RS 12n
Rewrite new bps starting in this pass
Rewrite new block pointers starting in this pass
.sp
Default value: \fB2\fR.
.RE
@ -1451,7 +1476,8 @@ Default value: \fB2\fR.
\fBzfs_top_maxinflight\fR (int)
.ad
.RS 12n
Max I/Os per top-level vdev during scrub or resilver operations.
Max concurrent I/Os per top-level vdev (mirrors or raidz arrays) allowed during
scrub or resilver operations.
.sp
Default value: \fB32\fR.
.RE
@ -1462,7 +1488,8 @@ Default value: \fB32\fR.
\fBzfs_txg_history\fR (int)
.ad
.RS 12n
Historic statistics for the last N txgs
Historic statistics for the last N txgs will be available in
\fR/proc/spl/kstat/zfs/POOLNAME/txgs\fB
.sp
Default value: \fB0\fR.
.RE
@ -1473,7 +1500,7 @@ Default value: \fB0\fR.
\fBzfs_txg_timeout\fR (int)
.ad
.RS 12n
Max seconds worth of delta per txg
Flush dirty data to disk at least every N seconds (maximum txg duration)
.sp
Default value: \fB5\fR.
.RE
@ -1497,7 +1524,7 @@ Default value: \fB131,072\fR.
.RS 12n
Shift size to inflate reads too
.sp
Default value: \fB16\fR.
Default value: \fB16\fR (effectively 65536).
.RE
.sp
@ -1506,7 +1533,10 @@ Default value: \fB16\fR.
\fBzfs_vdev_cache_max\fR (int)
.ad
.RS 12n
Inflate reads small than max
Inflate reads small than this value to meet the \fBzfs_vdev_cache_bshift\fR
size.
.sp
Default value: \fB16384\fR.
.RE
.sp
@ -1515,7 +1545,10 @@ Inflate reads small than max
\fBzfs_vdev_cache_size\fR (int)
.ad
.RS 12n
Total size of the per-disk cache
Total size of the per-disk cache in bytes.
.sp
Currently this feature is disabled as it has been found to not be helpful
for performance and in some cases harmful.
.sp
Default value: \fB0\fR.
.RE
@ -1596,7 +1629,8 @@ Default value: \fB1\fR.
\fBzfs_vdev_read_gap_limit\fR (int)
.ad
.RS 12n
Aggregate read I/O over gap
Aggregate read I/O operations if the gap on-disk between them is within this
threshold.
.sp
Default value: \fB32,768\fR.
.RE
@ -1607,7 +1641,7 @@ Default value: \fB32,768\fR.
\fBzfs_vdev_scheduler\fR (charp)
.ad
.RS 12n
I/O scheduler
Set the Linux I/O scheduler on whole disk vdevs to this scheduler
.sp
Default value: \fBnoop\fR.
.RE
@ -1629,7 +1663,7 @@ Default value: \fB4,096\fR.
\fBzfs_zevent_cols\fR (int)
.ad
.RS 12n
Max event column width
When zevents are logged to the console use this as the word wrap width.
.sp
Default value: \fB80\fR.
.RE
@ -1651,7 +1685,9 @@ Use \fB1\fR for yes and \fB0\fR for no (default).
\fBzfs_zevent_len_max\fR (int)
.ad
.RS 12n
Max event queue length
Max event queue length. A value of 0 will result in a calculated value which
increases with the number of CPUs in the system (minimum 64 events). Events
in the queue can be viewed with the \fBzpool events\fR command.
.sp
Default value: \fB0\fR.
.RE
@ -1662,7 +1698,8 @@ Default value: \fB0\fR.
\fBzil_replay_disable\fR (int)
.ad
.RS 12n
Disable intent logging replay
Disable intent logging replay. Can be disabled for recovery from corrupted
ZIL
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
@ -1684,7 +1721,9 @@ Default value: \fB1,048,576\fR.
\fBzio_delay_max\fR (int)
.ad
.RS 12n
Max zio millisecond delay before posting event
A zevent will be logged if a ZIO operation takes more than N milliseconds to
complete. Note that this is only a logging facility, not a timeout on
operations.
.sp
Default value: \fB30,000\fR.
.RE
@ -1723,7 +1762,8 @@ Default value: \fB75\fR.
\fBzvol_inhibit_dev\fR (uint)
.ad
.RS 12n
Do not create zvol device nodes
Do not create zvol device nodes. This may slightly improve startup time on
systems with a very large number of zvols.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
@ -1734,7 +1774,7 @@ Use \fB1\fR for yes and \fB0\fR for no (default).
\fBzvol_major\fR (uint)
.ad
.RS 12n
Major number for zvol device
Major number for zvol block devices
.sp
Default value: \fB230\fR.
.RE
@ -1745,7 +1785,9 @@ Default value: \fB230\fR.
\fBzvol_max_discard_blocks\fR (ulong)
.ad
.RS 12n
Max number of blocks to discard at once
Discard (aka TRIM) operations done on zvols will be done in batches of this
many blocks, where block size is determined by the \fBvolblocksize\fR property
of a zvol.
.sp
Default value: \fB16,384\fR.
.RE

2
man/man8/zfs.8
View File

@ -3782,6 +3782,6 @@ Invalid command line options were specified.
.SH SEE ALSO
.LP
\fBchmod\fR(2), \fBfsync\fR(2), \fBgzip\fR(1), \fBls\fR(1), \fBmount\fR(8), \fBopen\fR(2), \fBreaddir\fR(3), \fBssh\fR(1), \fBstat\fR(2), \fBwrite\fR(2), \fBzpool\fR(8)
\fBchmod\fR(2), \fBfsync\fR(2), \fBgzip\fR(1), \fBls\fR(1), \fBmount\fR(8), \fBopen\fR(2), \fBreaddir\fR(3), \fBssh\fR(1), \fBstat\fR(2), \fBwrite\fR(2), \fBzpool\fR(8), \fBzfs-module-parameters\fR(5)
.sp
On Solaris: \fBdfstab(4)\fR, \fBiscsitadm(1M)\fR, \fBmount(1M)\fR, \fBshare(1M)\fR, \fBsharemgr(1M)\fR, \fBunshare(1M)\fR

2
man/man8/zpool.8
View File

@ -2556,4 +2556,4 @@ them on \fBzpool create\fR or \fBzpool add\fR by setting ZFS_VDEV_DEVID_OPT_OUT.
.SH SEE ALSO
.sp
.LP
\fBzfs\fR(8), \fBzpool-features\fR(5), \fBzfs-events\fR(5)
\fBzfs\fR(8), \fBzpool-features\fR(5), \fBzfs-events\fR(5), \fBzfs-module-parameters\fR(5)