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aa7d06a98a
Today the metaslab_debug logic performs two tasks: - load all metaslabs on import/open - don't unload metaslabs at the end of spa_sync This change provides knobs for each of these independently. References: https://illumos.org/issues/4101 https://github.com/illumos/illumos-gate/commit/0713e23 Notes: 1) This is a small piece of the metaslab improvement patch from Illumos. It was worth bringing over before the rest, since it's low risk and it can be useful on fragmented pools (e.g. Lustre MDTs). metaslab_debug_unload would give the performance benefit of the old metaslab_debug option without causing unwanted delay during pool import. Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2227
1387 lines
28 KiB
Groff
1387 lines
28 KiB
Groff
'\" te
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.\" Copyright (c) 2013 by Turbo Fredriksson <turbo@bayour.com>. All rights reserved.
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.\" The contents of this file are subject to the terms of the Common Development
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.\" and Distribution License (the "License"). You may not use this file except
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.\" in compliance with the License. You can obtain a copy of the license at
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.\" usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.
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.\"
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.\" See the License for the specific language governing permissions and
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.\" limitations under the License. When distributing Covered Code, include this
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.\" CDDL HEADER in each file and include the License file at
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.\" usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this
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.\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
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.\" own identifying information:
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.\" Portions Copyright [yyyy] [name of copyright owner]
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.TH ZFS-MODULE-PARAMETERS 5 "Nov 16, 2013"
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.SH NAME
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zfs\-module\-parameters \- ZFS module parameters
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.SH DESCRIPTION
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.sp
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.LP
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Description of the different parameters to the ZFS module.
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.SS "Module parameters"
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.sp
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.LP
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.sp
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.ne 2
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.na
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|
\fBl2arc_feed_again\fR (int)
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|
.ad
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|
.RS 12n
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|
Turbo L2ARC warmup
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|
.sp
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|
Use \fB1\fR for yes (default) and \fB0\fR to disable.
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.RE
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.sp
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.ne 2
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.na
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|
\fBl2arc_feed_min_ms\fR (ulong)
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.ad
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.RS 12n
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|
Min feed interval in milliseconds
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.sp
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|
Default value: \fB200\fR.
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.RE
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|
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|
.sp
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.ne 2
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.na
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|
\fBl2arc_feed_secs\fR (ulong)
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|
.ad
|
|
.RS 12n
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|
Seconds between L2ARC writing
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|
.sp
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|
Default value: \fB1\fR.
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.RE
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|
|
|
.sp
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.ne 2
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|
.na
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|
\fBl2arc_headroom\fR (ulong)
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|
.ad
|
|
.RS 12n
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|
Number of max device writes to precache
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|
.sp
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|
Default value: \fB2\fR.
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.RE
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|
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|
.sp
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.ne 2
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.na
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|
\fBl2arc_headroom_boost\fR (ulong)
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|
.ad
|
|
.RS 12n
|
|
Compressed l2arc_headroom multiplier
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|
.sp
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|
Default value: \fB200\fR.
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.RE
|
|
|
|
.sp
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.ne 2
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.na
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|
\fBl2arc_nocompress\fR (int)
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|
.ad
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|
.RS 12n
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|
Skip compressing L2ARC buffers
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.sp
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|
Use \fB1\fR for yes and \fB0\fR for no (default).
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.RE
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.sp
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.ne 2
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|
.na
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|
\fBl2arc_noprefetch\fR (int)
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|
.ad
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|
.RS 12n
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|
Skip caching prefetched buffers
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.sp
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|
Use \fB1\fR for yes (default) and \fB0\fR to disable.
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.RE
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.sp
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.ne 2
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|
.na
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|
\fBl2arc_norw\fR (int)
|
|
.ad
|
|
.RS 12n
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|
No reads during writes
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.sp
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|
Use \fB1\fR for yes and \fB0\fR for no (default).
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.RE
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|
|
|
.sp
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.ne 2
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.na
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|
\fBl2arc_write_boost\fR (ulong)
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|
.ad
|
|
.RS 12n
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|
Extra write bytes during device warmup
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|
.sp
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|
Default value: \fB8,388,608\fR.
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.RE
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|
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|
.sp
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.ne 2
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.na
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|
\fBl2arc_write_max\fR (ulong)
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|
.ad
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|
.RS 12n
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|
Max write bytes per interval
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|
.sp
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|
Default value: \fB8,388,608\fR.
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.RE
|
|
|
|
.sp
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.ne 2
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.na
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|
\fBmetaslab_debug_load\fR (int)
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|
.ad
|
|
.RS 12n
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|
Load all metaslabs during pool import.
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|
.sp
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|
Use \fB1\fR for yes and \fB0\fR for no (default).
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.RE
|
|
|
|
.sp
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|
.ne 2
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.na
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|
\fBmetaslab_debug_unload\fR (int)
|
|
.ad
|
|
.RS 12n
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|
Prevent metaslabs from being unloaded.
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|
.sp
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|
Use \fB1\fR for yes and \fB0\fR for no (default).
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.RE
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|
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|
.sp
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.ne 2
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|
.na
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|
\fBspa_config_path\fR (charp)
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|
.ad
|
|
.RS 12n
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|
SPA config file
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|
.sp
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|
Default value: \fB/etc/zfs/zpool.cache\fR.
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.RE
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|
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|
.sp
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.ne 2
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.na
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|
\fBspa_asize_inflation\fR (int)
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|
.ad
|
|
.RS 12n
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|
Multiplication factor used to estimate actual disk consumption from the
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size of data being written. The default value is a worst case estimate,
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but lower values may be valid for a given pool depending on its
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configuration. Pool administrators who understand the factors involved
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may wish to specify a more realistic inflation factor, particularly if
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they operate close to quota or capacity limits.
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.sp
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|
Default value: 24
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.RE
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|
|
|
.sp
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|
.ne 2
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|
.na
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|
\fBzfetch_array_rd_sz\fR (ulong)
|
|
.ad
|
|
.RS 12n
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|
Number of bytes in a array_read
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|
.sp
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|
Default value: \fB1,048,576\fR.
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.RE
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|
|
|
.sp
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.ne 2
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.na
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|
\fBzfetch_block_cap\fR (uint)
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|
.ad
|
|
.RS 12n
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|
Max number of blocks to fetch at a time
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|
.sp
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|
Default value: \fB256\fR.
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.RE
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|
|
|
.sp
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.ne 2
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.na
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|
\fBzfetch_max_streams\fR (uint)
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|
.ad
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|
.RS 12n
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|
Max number of streams per zfetch
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|
.sp
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|
Default value: \fB8\fR.
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.RE
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|
|
|
.sp
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.ne 2
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.na
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|
\fBzfetch_min_sec_reap\fR (uint)
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|
.ad
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.RS 12n
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|
Min time before stream reclaim
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.sp
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|
Default value: \fB2\fR.
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.RE
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|
|
|
.sp
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.ne 2
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.na
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|
\fBzfs_arc_grow_retry\fR (int)
|
|
.ad
|
|
.RS 12n
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|
Seconds before growing arc size
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|
.sp
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|
Default value: \fB5\fR.
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.RE
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|
|
|
.sp
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|
.ne 2
|
|
.na
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|
\fBzfs_arc_max\fR (ulong)
|
|
.ad
|
|
.RS 12n
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|
Max arc size
|
|
.sp
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|
Default value: \fB0\fR.
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|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_arc_memory_throttle_disable\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Disable memory throttle
|
|
.sp
|
|
Use \fB1\fR for yes (default) and \fB0\fR to disable.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_arc_meta_limit\fR (ulong)
|
|
.ad
|
|
.RS 12n
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|
Meta limit for arc size
|
|
.sp
|
|
Default value: \fB0\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_arc_meta_prune\fR (int)
|
|
.ad
|
|
.RS 12n
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|
Bytes of meta data to prune
|
|
.sp
|
|
Default value: \fB1,048,576\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_arc_min\fR (ulong)
|
|
.ad
|
|
.RS 12n
|
|
Min arc size
|
|
.sp
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|
Default value: \fB100\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_arc_min_prefetch_lifespan\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Min life of prefetch block
|
|
.sp
|
|
Default value: \fB100\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_arc_p_aggressive_disable\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Disable aggressive arc_p growth
|
|
.sp
|
|
Use \fB1\fR for yes (default) and \fB0\fR to disable.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_arc_p_dampener_disable\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Disable arc_p adapt dampener
|
|
.sp
|
|
Use \fB1\fR for yes (default) and \fB0\fR to disable.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_arc_shrink_shift\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
log2(fraction of arc to reclaim)
|
|
.sp
|
|
Default value: \fB5\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_autoimport_disable\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Disable pool import at module load
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_dbuf_state_index\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Calculate arc header index
|
|
.sp
|
|
Default value: \fB0\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_deadman_enabled\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Enable deadman timer
|
|
.sp
|
|
Use \fB1\fR for yes (default) and \fB0\fR to disable.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_deadman_synctime_ms\fR (ulong)
|
|
.ad
|
|
.RS 12n
|
|
Expiration time in milliseconds. This value has two meanings. First it is
|
|
used to determine when the spa_deadman() logic should fire. By default the
|
|
spa_deadman() will fire if spa_sync() has not completed in 1000 seconds.
|
|
Secondly, the value determines if an I/O is considered "hung". Any I/O that
|
|
has not completed in zfs_deadman_synctime_ms is considered "hung" resulting
|
|
in a zevent being logged.
|
|
.sp
|
|
Default value: \fB1,000,000\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_dedup_prefetch\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Enable prefetching dedup-ed blks
|
|
.sp
|
|
Use \fB1\fR for yes (default) and \fB0\fR to disable.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_delay_min_dirty_percent\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Start to delay each transaction once there is this amount of dirty data,
|
|
expressed as a percentage of \fBzfs_dirty_data_max\fR.
|
|
This value should be >= zfs_vdev_async_write_active_max_dirty_percent.
|
|
See the section "ZFS TRANSACTION DELAY".
|
|
.sp
|
|
Default value: \fB60\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_delay_scale\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
This controls how quickly the transaction delay approaches infinity.
|
|
Larger values cause longer delays for a given amount of dirty data.
|
|
.sp
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|
For the smoothest delay, this value should be about 1 billion divided
|
|
by the maximum number of operations per second. This will smoothly
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|
handle between 10x and 1/10th this number.
|
|
.sp
|
|
See the section "ZFS TRANSACTION DELAY".
|
|
.sp
|
|
Note: \fBzfs_delay_scale\fR * \fBzfs_dirty_data_max\fR must be < 2^64.
|
|
.sp
|
|
Default value: \fB500,000\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
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|
\fBzfs_dirty_data_max\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Determines the dirty space limit in bytes. Once this limit is exceeded, new
|
|
writes are halted until space frees up. This parameter takes precedence
|
|
over \fBzfs_dirty_data_max_percent\fR.
|
|
See the section "ZFS TRANSACTION DELAY".
|
|
.sp
|
|
Default value: 10 percent of all memory, capped at \fBzfs_dirty_data_max_max\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_dirty_data_max_max\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Maximum allowable value of \fBzfs_dirty_data_max\fR, expressed in bytes.
|
|
This limit is only enforced at module load time, and will be ignored if
|
|
\fBzfs_dirty_data_max\fR is later changed. This parameter takes
|
|
precedence over \fBzfs_dirty_data_max_max_percent\fR. See the section
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|
"ZFS TRANSACTION DELAY".
|
|
.sp
|
|
Default value: 25% of physical RAM.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_dirty_data_max_max_percent\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Maximum allowable value of \fBzfs_dirty_data_max\fR, expressed as a
|
|
percentage of physical RAM. This limit is only enforced at module load
|
|
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
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_dirty_data_max_percent\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Determines the dirty space limit, expressed as a percentage of all
|
|
memory. Once this limit is exceeded, new writes are halted until space frees
|
|
up. The parameter \fBzfs_dirty_data_max\fR takes precedence over this
|
|
one. See the section "ZFS TRANSACTION DELAY".
|
|
.sp
|
|
Default value: 10%, subject to \fBzfs_dirty_data_max_max\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_dirty_data_sync\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Start syncing out a transaction group if there is at least this much dirty data.
|
|
.sp
|
|
Default value: \fB67,108,864\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_async_read_max_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Maxium asynchronous read I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB3\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_async_read_min_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Minimum asynchronous read I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB1\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_async_write_active_max_dirty_percent\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
When the pool has more than
|
|
\fBzfs_vdev_async_write_active_max_dirty_percent\fR dirty data, use
|
|
\fBzfs_vdev_async_write_max_active\fR to limit active async writes. If
|
|
the dirty data is between min and max, the active I/O limit is linearly
|
|
interpolated. See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB60\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_async_write_active_min_dirty_percent\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
When the pool has less than
|
|
\fBzfs_vdev_async_write_active_min_dirty_percent\fR dirty data, use
|
|
\fBzfs_vdev_async_write_min_active\fR to limit active async writes. If
|
|
the dirty data is between min and max, the active I/O limit is linearly
|
|
interpolated. See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB30\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_async_write_max_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Maxium asynchronous write I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB10\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_async_write_min_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Minimum asynchronous write I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB1\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_max_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
The maximum number of I/Os active to each device. Ideally, this will be >=
|
|
the sum of each queue's max_active. It must be at least the sum of each
|
|
queue's min_active. See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB1,000\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_scrub_max_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Maxium scrub I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB2\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_scrub_min_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Minimum scrub I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB1\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_sync_read_max_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Maxium synchronous read I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB10\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_sync_read_min_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Minimum synchronous read I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB10\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_sync_write_max_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Maxium synchronous write I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB10\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_sync_write_min_active\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Minimum synchronous write I/Os active to each device.
|
|
See the section "ZFS I/O SCHEDULER".
|
|
.sp
|
|
Default value: \fB10\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_disable_dup_eviction\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Disable duplicate buffer eviction
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_expire_snapshot\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Seconds to expire .zfs/snapshot
|
|
.sp
|
|
Default value: \fB300\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_flags\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Set additional debugging flags
|
|
.sp
|
|
Default value: \fB1\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_free_min_time_ms\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Min millisecs to free per txg
|
|
.sp
|
|
Default value: \fB1,000\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_immediate_write_sz\fR (long)
|
|
.ad
|
|
.RS 12n
|
|
Largest data block to write to zil
|
|
.sp
|
|
Default value: \fB32,768\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_mdcomp_disable\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Disable meta data compression
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_no_scrub_io\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Set for no scrub I/O
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_no_scrub_prefetch\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Set for no scrub prefetching
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_nocacheflush\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Disable cache flushes
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_nopwrite_enabled\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Enable NOP writes
|
|
.sp
|
|
Use \fB1\fR for yes (default) and \fB0\fR to disable.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_pd_blks_max\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Max number of blocks to prefetch
|
|
.sp
|
|
Default value: \fB100\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_prefetch_disable\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Disable all ZFS prefetching
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_read_chunk_size\fR (long)
|
|
.ad
|
|
.RS 12n
|
|
Bytes to read per chunk
|
|
.sp
|
|
Default value: \fB1,048,576\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_read_history\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Historic statistics for the last N reads
|
|
.sp
|
|
Default value: \fB0\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_read_history_hits\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Include cache hits in read history
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_recover\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Set to attempt to recover from fatal errors. This should only be used as a
|
|
last resort, as it typically results in leaked space, or worse.
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_resilver_delay\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Number of ticks to delay resilver
|
|
.sp
|
|
Default value: \fB2\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_resilver_min_time_ms\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Min millisecs to resilver per txg
|
|
.sp
|
|
Default value: \fB3,000\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_scan_idle\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Idle window in clock ticks
|
|
.sp
|
|
Default value: \fB50\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_scan_min_time_ms\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Min millisecs to scrub per txg
|
|
.sp
|
|
Default value: \fB1,000\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_scrub_delay\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Number of ticks to delay scrub
|
|
.sp
|
|
Default value: \fB4\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_send_corrupt_data\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Allow to send corrupt data (ignore read/checksum errors when sending data)
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_sync_pass_deferred_free\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Defer frees starting in this pass
|
|
.sp
|
|
Default value: \fB2\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_sync_pass_dont_compress\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Don't compress starting in this pass
|
|
.sp
|
|
Default value: \fB5\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_sync_pass_rewrite\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Rewrite new bps starting in this pass
|
|
.sp
|
|
Default value: \fB2\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_top_maxinflight\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Max I/Os per top-level
|
|
.sp
|
|
Default value: \fB32\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_txg_history\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Historic statistics for the last N txgs
|
|
.sp
|
|
Default value: \fB0\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_txg_timeout\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Max seconds worth of delta per txg
|
|
.sp
|
|
Default value: \fB5\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_aggregation_limit\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Max vdev I/O aggregation size
|
|
.sp
|
|
Default value: \fB131,072\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_cache_bshift\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Shift size to inflate reads too
|
|
.sp
|
|
Default value: \fB16\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_cache_max\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Inflate reads small than max
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_cache_size\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Total size of the per-disk cache
|
|
.sp
|
|
Default value: \fB0\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_mirror_switch_us\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Switch mirrors every N usecs
|
|
.sp
|
|
Default value: \fB10,000\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_read_gap_limit\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Aggregate read I/O over gap
|
|
.sp
|
|
Default value: \fB32,768\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_scheduler\fR (charp)
|
|
.ad
|
|
.RS 12n
|
|
I/O scheduler
|
|
.sp
|
|
Default value: \fBnoop\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_vdev_write_gap_limit\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Aggregate write I/O over gap
|
|
.sp
|
|
Default value: \fB4,096\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_zevent_cols\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Max event column width
|
|
.sp
|
|
Default value: \fB80\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_zevent_console\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Log events to the console
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzfs_zevent_len_max\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Max event queue length
|
|
.sp
|
|
Default value: \fB0\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzil_replay_disable\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Disable intent logging replay
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzil_slog_limit\fR (ulong)
|
|
.ad
|
|
.RS 12n
|
|
Max commit bytes to separate log device
|
|
.sp
|
|
Default value: \fB1,048,576\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzio_bulk_flags\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Additional flags to pass to bulk buffers
|
|
.sp
|
|
Default value: \fB0\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzio_delay_max\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Max zio millisec delay before posting event
|
|
.sp
|
|
Default value: \fB30,000\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzio_injection_enabled\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Enable fault injection
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzio_requeue_io_start_cut_in_line\fR (int)
|
|
.ad
|
|
.RS 12n
|
|
Prioritize requeued I/O
|
|
.sp
|
|
Default value: \fB0\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzvol_inhibit_dev\fR (uint)
|
|
.ad
|
|
.RS 12n
|
|
Do not create zvol device nodes
|
|
.sp
|
|
Use \fB1\fR for yes and \fB0\fR for no (default).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzvol_major\fR (uint)
|
|
.ad
|
|
.RS 12n
|
|
Major number for zvol device
|
|
.sp
|
|
Default value: \fB230\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzvol_max_discard_blocks\fR (ulong)
|
|
.ad
|
|
.RS 12n
|
|
Max number of blocks to discard at once
|
|
.sp
|
|
Default value: \fB16,384\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzvol_threads\fR (uint)
|
|
.ad
|
|
.RS 12n
|
|
Number of threads for zvol device
|
|
.sp
|
|
Default value: \fB32\fR.
|
|
.RE
|
|
|
|
.SH ZFS I/O SCHEDULER
|
|
ZFS issues I/O operations to leaf vdevs to satisfy and complete I/Os.
|
|
The I/O scheduler determines when and in what order those operations are
|
|
issued. The I/O scheduler divides operations into five I/O classes
|
|
prioritized in the following order: sync read, sync write, async read,
|
|
async write, and scrub/resilver. Each queue defines the minimum and
|
|
maximum number of concurrent operations that may be issued to the
|
|
device. In addition, the device has an aggregate maximum,
|
|
\fBzfs_vdev_max_active\fR. Note that the sum of the per-queue minimums
|
|
must not exceed the aggregate maximum. If the sum of the per-queue
|
|
maximums exceeds the aggregate maximum, then the number of active I/Os
|
|
may reach \fBzfs_vdev_max_active\fR, in which case no further I/Os will
|
|
be issued regardless of whether all per-queue minimums have been met.
|
|
.sp
|
|
For many physical devices, throughput increases with the number of
|
|
concurrent operations, but latency typically suffers. Further, physical
|
|
devices typically have a limit at which more concurrent operations have no
|
|
effect on throughput or can actually cause it to decrease.
|
|
.sp
|
|
The scheduler selects the next operation to issue by first looking for an
|
|
I/O class whose minimum has not been satisfied. Once all are satisfied and
|
|
the aggregate maximum has not been hit, the scheduler looks for classes
|
|
whose maximum has not been satisfied. Iteration through the I/O classes is
|
|
done in the order specified above. No further operations are issued if the
|
|
aggregate maximum number of concurrent operations has been hit or if there
|
|
are no operations queued for an I/O class that has not hit its maximum.
|
|
Every time an I/O is queued or an operation completes, the I/O scheduler
|
|
looks for new operations to issue.
|
|
.sp
|
|
In general, smaller max_active's will lead to lower latency of synchronous
|
|
operations. Larger max_active's may lead to higher overall throughput,
|
|
depending on underlying storage.
|
|
.sp
|
|
The ratio of the queues' max_actives determines the balance of performance
|
|
between reads, writes, and scrubs. E.g., increasing
|
|
\fBzfs_vdev_scrub_max_active\fR will cause the scrub or resilver to complete
|
|
more quickly, but reads and writes to have higher latency and lower throughput.
|
|
.sp
|
|
All I/O classes have a fixed maximum number of outstanding operations
|
|
except for the async write class. Asynchronous writes represent the data
|
|
that is committed to stable storage during the syncing stage for
|
|
transaction groups. Transaction groups enter the syncing state
|
|
periodically so the number of queued async writes will quickly burst up
|
|
and then bleed down to zero. Rather than servicing them as quickly as
|
|
possible, the I/O scheduler changes the maximum number of active async
|
|
write I/Os according to the amount of dirty data in the pool. Since
|
|
both throughput and latency typically increase with the number of
|
|
concurrent operations issued to physical devices, reducing the
|
|
burstiness in the number of concurrent operations also stabilizes the
|
|
response time of operations from other -- and in particular synchronous
|
|
-- queues. In broad strokes, the I/O scheduler will issue more
|
|
concurrent operations from the async write queue as there's more dirty
|
|
data in the pool.
|
|
.sp
|
|
Async Writes
|
|
.sp
|
|
The number of concurrent operations issued for the async write I/O class
|
|
follows a piece-wise linear function defined by a few adjustable points.
|
|
.nf
|
|
|
|
| o---------| <-- zfs_vdev_async_write_max_active
|
|
^ | /^ |
|
|
| | / | |
|
|
active | / | |
|
|
I/O | / | |
|
|
count | / | |
|
|
| / | |
|
|
|-------o | | <-- zfs_vdev_async_write_min_active
|
|
0|_______^______|_________|
|
|
0% | | 100% of zfs_dirty_data_max
|
|
| |
|
|
| `-- zfs_vdev_async_write_active_max_dirty_percent
|
|
`--------- zfs_vdev_async_write_active_min_dirty_percent
|
|
|
|
.fi
|
|
Until the amount of dirty data exceeds a minimum percentage of the dirty
|
|
data allowed in the pool, the I/O scheduler will limit the number of
|
|
concurrent operations to the minimum. As that threshold is crossed, the
|
|
number of concurrent operations issued increases linearly to the maximum at
|
|
the specified maximum percentage of the dirty data allowed in the pool.
|
|
.sp
|
|
Ideally, the amount of dirty data on a busy pool will stay in the sloped
|
|
part of the function between \fBzfs_vdev_async_write_active_min_dirty_percent\fR
|
|
and \fBzfs_vdev_async_write_active_max_dirty_percent\fR. If it exceeds the
|
|
maximum percentage, this indicates that the rate of incoming data is
|
|
greater than the rate that the backend storage can handle. In this case, we
|
|
must further throttle incoming writes, as described in the next section.
|
|
|
|
.SH ZFS TRANSACTION DELAY
|
|
We delay transactions when we've determined that the backend storage
|
|
isn't able to accommodate the rate of incoming writes.
|
|
.sp
|
|
If there is already a transaction waiting, we delay relative to when
|
|
that transaction will finish waiting. This way the calculated delay time
|
|
is independent of the number of threads concurrently executing
|
|
transactions.
|
|
.sp
|
|
If we are the only waiter, wait relative to when the transaction
|
|
started, rather than the current time. This credits the transaction for
|
|
"time already served", e.g. reading indirect blocks.
|
|
.sp
|
|
The minimum time for a transaction to take is calculated as:
|
|
.nf
|
|
min_time = zfs_delay_scale * (dirty - min) / (max - dirty)
|
|
min_time is then capped at 100 milliseconds.
|
|
.fi
|
|
.sp
|
|
The delay has two degrees of freedom that can be adjusted via tunables. The
|
|
percentage of dirty data at which we start to delay is defined by
|
|
\fBzfs_delay_min_dirty_percent\fR. This should typically be at or above
|
|
\fBzfs_vdev_async_write_active_max_dirty_percent\fR so that we only start to
|
|
delay after writing at full speed has failed to keep up with the incoming write
|
|
rate. The scale of the curve is defined by \fBzfs_delay_scale\fR. Roughly speaking,
|
|
this variable determines the amount of delay at the midpoint of the curve.
|
|
.sp
|
|
.nf
|
|
delay
|
|
10ms +-------------------------------------------------------------*+
|
|
| *|
|
|
9ms + *+
|
|
| *|
|
|
8ms + *+
|
|
| * |
|
|
7ms + * +
|
|
| * |
|
|
6ms + * +
|
|
| * |
|
|
5ms + * +
|
|
| * |
|
|
4ms + * +
|
|
| * |
|
|
3ms + * +
|
|
| * |
|
|
2ms + (midpoint) * +
|
|
| | ** |
|
|
1ms + v *** +
|
|
| zfs_delay_scale ----------> ******** |
|
|
0 +-------------------------------------*********----------------+
|
|
0% <- zfs_dirty_data_max -> 100%
|
|
.fi
|
|
.sp
|
|
Note that since the delay is added to the outstanding time remaining on the
|
|
most recent transaction, the delay is effectively the inverse of IOPS.
|
|
Here the midpoint of 500us translates to 2000 IOPS. The shape of the curve
|
|
was chosen such that small changes in the amount of accumulated dirty data
|
|
in the first 3/4 of the curve yield relatively small differences in the
|
|
amount of delay.
|
|
.sp
|
|
The effects can be easier to understand when the amount of delay is
|
|
represented on a log scale:
|
|
.sp
|
|
.nf
|
|
delay
|
|
100ms +-------------------------------------------------------------++
|
|
+ +
|
|
| |
|
|
+ *+
|
|
10ms + *+
|
|
+ ** +
|
|
| (midpoint) ** |
|
|
+ | ** +
|
|
1ms + v **** +
|
|
+ zfs_delay_scale ----------> ***** +
|
|
| **** |
|
|
+ **** +
|
|
100us + ** +
|
|
+ * +
|
|
| * |
|
|
+ * +
|
|
10us + * +
|
|
+ +
|
|
| |
|
|
+ +
|
|
+--------------------------------------------------------------+
|
|
0% <- zfs_dirty_data_max -> 100%
|
|
.fi
|
|
.sp
|
|
Note here that only as the amount of dirty data approaches its limit does
|
|
the delay start to increase rapidly. The goal of a properly tuned system
|
|
should be to keep the amount of dirty data out of that range by first
|
|
ensuring that the appropriate limits are set for the I/O scheduler to reach
|
|
optimal throughput on the backend storage, and then by changing the value
|
|
of \fBzfs_delay_scale\fR to increase the steepness of the curve.
|