'\" te
.\" Copyright (c) 2013 by Turbo Fredriksson <turbo@bayour.com>. All rights reserved.
.\" The contents of this file are subject to the terms of the Common Development
.\" and Distribution License (the "License").  You may not use this file except
.\" in compliance with the License. You can obtain a copy of the license at
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.\"
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.\" limitations under the License. When distributing Covered Code, include this
.\" CDDL HEADER in each file and include the License file at
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.\" Portions Copyright [yyyy] [name of copyright owner]
.TH ZFS-MODULE-PARAMETERS 5 "Nov 16, 2013"
.SH NAME
zfs\-module\-parameters \- ZFS module parameters
.SH DESCRIPTION
.sp
.LP
Description of the different parameters to the ZFS module.

.SS "Module parameters"
.sp
.LP

.sp
.ne 2
.na
\fBl2arc_feed_again\fR (int)
.ad
.RS 12n
Turbo L2ARC warmup
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE

.sp
.ne 2
.na
\fBl2arc_feed_min_ms\fR (ulong)
.ad
.RS 12n
Min feed interval in milliseconds
.sp
Default value: \fB200\fR.
.RE

.sp
.ne 2
.na
\fBl2arc_feed_secs\fR (ulong)
.ad
.RS 12n
Seconds between L2ARC writing
.sp
Default value: \fB1\fR.
.RE

.sp
.ne 2
.na
\fBl2arc_headroom\fR (ulong)
.ad
.RS 12n
Number of max device writes to precache
.sp
Default value: \fB2\fR.
.RE

.sp
.ne 2
.na
\fBl2arc_headroom_boost\fR (ulong)
.ad
.RS 12n
Compressed l2arc_headroom multiplier
.sp
Default value: \fB200\fR.
.RE

.sp
.ne 2
.na
\fBl2arc_nocompress\fR (int)
.ad
.RS 12n
Skip compressing L2ARC buffers
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE

.sp
.ne 2
.na
\fBl2arc_noprefetch\fR (int)
.ad
.RS 12n
Skip caching prefetched buffers
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE

.sp
.ne 2
.na
\fBl2arc_norw\fR (int)
.ad
.RS 12n
No reads during writes
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE

.sp
.ne 2
.na
\fBl2arc_write_boost\fR (ulong)
.ad
.RS 12n
Extra write bytes during device warmup
.sp
Default value: \fB8,388,608\fR.
.RE

.sp
.ne 2
.na
\fBl2arc_write_max\fR (ulong)
.ad
.RS 12n
Max write bytes per interval
.sp
Default value: \fB8,388,608\fR.
.RE

.sp
.ne 2
.na
\fBmetaslab_debug\fR (int)
.ad
.RS 12n
Keep space maps in core to verify frees
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE

.sp
.ne 2
.na
\fBspa_config_path\fR (charp)
.ad
.RS 12n
SPA config file
.sp
Default value: \fB/etc/zfs/zpool.cache\fR.
.RE

.sp
.ne 2
.na
\fBzfetch_array_rd_sz\fR (ulong)
.ad
.RS 12n
Number of bytes in a array_read
.sp
Default value: \fB1,048,576\fR.
.RE

.sp
.ne 2
.na
\fBzfetch_block_cap\fR (uint)
.ad
.RS 12n
Max number of blocks to fetch at a time
.sp
Default value: \fB256\fR.
.RE

.sp
.ne 2
.na
\fBzfetch_max_streams\fR (uint)
.ad
.RS 12n
Max number of streams per zfetch
.sp
Default value: \fB8\fR.
.RE

.sp
.ne 2
.na
\fBzfetch_min_sec_reap\fR (uint)
.ad
.RS 12n
Min time before stream reclaim
.sp
Default value: \fB2\fR.
.RE

.sp
.ne 2
.na
\fBzfs_arc_grow_retry\fR (int)
.ad
.RS 12n
Seconds before growing arc size
.sp
Default value: \fB5\fR.
.RE

.sp
.ne 2
.na
\fBzfs_arc_max\fR (ulong)
.ad
.RS 12n
Max arc size
.sp
Default value: \fB0\fR.
.RE

.sp
.ne 2
.na
\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
\fBzfs_arc_meta_limit\fR (ulong)
.ad
.RS 12n
Meta limit for arc size
.sp
Default value: \fB0\fR.
.RE

.sp
.ne 2
.na
\fBzfs_arc_meta_prune\fR (int)
.ad
.RS 12n
Bytes of meta data to prune
.sp
Default value: \fB1,048,576\fR.
.RE

.sp
.ne 2
.na
\fBzfs_arc_min\fR (ulong)
.ad
.RS 12n
Min arc size
.sp
Default value: \fB100\fR.
.RE

.sp
.ne 2
.na
\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
\fBzfs_arc_p_min_shift\fR (int)
.ad
.RS 12n
arc_c shift to calc min/max arc_p
.sp
Default value: \fB4\fR.
.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
\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
\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
\fBzfs_deadman_synctime\fR (ulong)
.ad
.RS 12n
Expire in units of zfs_txg_synctime_ms
.sp
Default value: \fB1,000\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_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_no_write_throttle\fR (int)
.ad
.RS 12n
Disable write throttling
.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_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_synctime_ms\fR (int)
.ad
.RS 12n
Target milliseconds between txg sync
.sp
Default value: \fB1,000\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_max_pending\fR (int)
.ad
.RS 12n
Max pending per-vdev I/Os
.sp
Default value: \fB10\fR.
.RE

.sp
.ne 2
.na
\fBzfs_vdev_min_pending\fR (int)
.ad
.RS 12n
Min pending per-vdev I/Os
.sp
Default value: \fB4\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_ramp_rate\fR (int)
.ad
.RS 12n
Exponential I/O issue ramp-up rate
.sp
Default value: \fB2\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_time_shift\fR (int)
.ad
.RS 12n
Deadline time shift for vdev I/O
.sp
Default value: \fB29\fR (each bucket is 0.537 seconds).
.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_write_limit_inflated\fR (ulong)
.ad
.RS 12n
Inflated txg write limit
.sp
Default value: \fB0\fR.
.RE

.sp
.ne 2
.na
\fBzfs_write_limit_max\fR (ulong)
.ad
.RS 12n
Max txg write limit
.sp
Default value: \fB0\fR.
.RE

.sp
.ne 2
.na
\fBzfs_write_limit_min\fR (ulong)
.ad
.RS 12n
Min txg write limit
.sp
Default value: \fB33,554,432\fR.
.RE

.sp
.ne 2
.na
\fBzfs_write_limit_override\fR (ulong)
.ad
.RS 12n
Override txg write limit
.sp
Default value: \fB0\fR.
.RE

.sp
.ne 2
.na
\fBzfs_write_limit_shift\fR (int)
.ad
.RS 12n
log2(fraction of memory) per txg
.sp
Default value: \fB3\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