freebsd-dev/man/man5/zfs-module-parameters.5

'\" te
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.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