'\" te
.\" Copyright (c) 2013 by Turbo Fredriksson <turbo@bayour.com>. All rights reserved.
+.\" Copyright (c) 2019 by Delphix. All rights reserved.
+.\" Copyright (c) 2019 Datto Inc.
.\" 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
.\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
.\" own identifying information:
.\" Portions Copyright [yyyy] [name of copyright owner]
-.TH ZFS-MODULE-PARAMETERS 5 "Nov 16, 2013"
+.TH ZFS-MODULE-PARAMETERS 5 "Feb 15, 2019"
.SH NAME
zfs\-module\-parameters \- ZFS module parameters
.SH DESCRIPTION
.sp
.LP
+.sp
+.ne 2
+.na
+\fBdbuf_cache_max_bytes\fR (ulong)
+.ad
+.RS 12n
+Maximum size in bytes of the dbuf cache. When \fB0\fR this value will default
+to \fB1/2^dbuf_cache_shift\fR (1/32) of the target ARC size, otherwise the
+provided value in bytes will be used. The behavior of the dbuf cache and its
+associated settings can be observed via the \fB/proc/spl/kstat/zfs/dbufstats\fR
+kstat.
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBdbuf_metadata_cache_max_bytes\fR (ulong)
+.ad
+.RS 12n
+Maximum size in bytes of the metadata dbuf cache. When \fB0\fR this value will
+default to \fB1/2^dbuf_cache_shift\fR (1/16) of the target ARC size, otherwise
+the provided value in bytes will be used. The behavior of the metadata dbuf
+cache and its associated settings can be observed via the
+\fB/proc/spl/kstat/zfs/dbufstats\fR kstat.
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBdbuf_cache_hiwater_pct\fR (uint)
+.ad
+.RS 12n
+The percentage over \fBdbuf_cache_max_bytes\fR when dbufs must be evicted
+directly.
+.sp
+Default value: \fB10\fR%.
+.RE
+
+.sp
+.ne 2
+.na
+\fBdbuf_cache_lowater_pct\fR (uint)
+.ad
+.RS 12n
+The percentage below \fBdbuf_cache_max_bytes\fR when the evict thread stops
+evicting dbufs.
+.sp
+Default value: \fB10\fR%.
+.RE
+
+.sp
+.ne 2
+.na
+\fBdbuf_cache_shift\fR (int)
+.ad
+.RS 12n
+Set the size of the dbuf cache, \fBdbuf_cache_max_bytes\fR, to a log2 fraction
+of the target arc size.
+.sp
+Default value: \fB5\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBdbuf_metadata_cache_shift\fR (int)
+.ad
+.RS 12n
+Set the size of the dbuf metadata cache, \fBdbuf_metadata_cache_max_bytes\fR,
+to a log2 fraction of the target arc size.
+.sp
+Default value: \fB6\fR.
+.RE
+
.sp
.ne 2
.na
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
-
-.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).
+Default value: \fB200\fR%.
.RE
.sp
\fBl2arc_write_boost\fR (ulong)
.ad
.RS 12n
-Cold L2ARC devices will have \fBl2arc_write_nax\fR increased by this amount
+Cold L2ARC devices will have \fBl2arc_write_max\fR increased by this amount
while they remain cold.
.sp
Default value: \fB8,388,608\fR.
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
+.sp
+.ne 2
+.na
+\fBmetaslab_force_ganging\fR (ulong)
+.ad
+.RS 12n
+Make some blocks above a certain size be gang blocks. This option is used
+by the test suite to facilitate testing.
+.sp
+Default value: \fB16,777,217\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_metaslab_segment_weight_enabled\fR (int)
+.ad
+.RS 12n
+Enable/disable segment-based metaslab selection.
+.sp
+Use \fB1\fR for yes (default) and \fB0\fR for no.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_metaslab_switch_threshold\fR (int)
+.ad
+.RS 12n
+When using segment-based metaslab selection, continue allocating
+from the active metaslab until \fBzfs_metaslab_switch_threshold\fR
+worth of buckets have been exhausted.
+.sp
+Default value: \fB2\fR.
+.RE
+
.sp
.ne 2
.na
.sp
.ne 2
.na
-\fBmetaslabs_per_vdev\fR (int)
+\fBzfs_vdev_default_ms_count\fR (int)
.ad
.RS 12n
-When a vdev is added, it will be divided into approximately (but no more than) this number of metaslabs.
+When a vdev is added target this number of metaslabs per top-level vdev.
.sp
Default value: \fB200\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_vdev_min_ms_count\fR (int)
+.ad
+.RS 12n
+Minimum number of metaslabs to create in a top-level vdev.
+.sp
+Default value: \fB16\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBvdev_ms_count_limit\fR (int)
+.ad
+.RS 12n
+Practical upper limit of total metaslabs per top-level vdev.
+.sp
+Default value: \fB131,072\fR.
+.RE
+
.sp
.ne 2
.na
Default value: \fB24\fR.
.RE
+.sp
+.ne 2
+.na
+\fBspa_load_print_vdev_tree\fR (int)
+.ad
+.RS 12n
+Whether to print the vdev tree in the debugging message buffer during pool import.
+Use 0 to disable and 1 to enable.
+.sp
+Default value: \fB0\fR.
+.RE
+
.sp
.ne 2
.na
Default value: \fB5\fR.
.RE
+.sp
+.ne 2
+.na
+\fBvdev_removal_max_span\fR (int)
+.ad
+.RS 12n
+During top-level vdev removal, chunks of data are copied from the vdev
+which may include free space in order to trade bandwidth for IOPS.
+This parameter determines the maximum span of free space (in bytes)
+which will be included as "unnecessary" data in a chunk of copied data.
+
+The default value here was chosen to align with
+\fBzfs_vdev_read_gap_limit\fR, which is a similar concept when doing
+regular reads (but there's no reason it has to be the same).
+.sp
+Default value: \fB32,768\fR.
+.RE
+
.sp
.ne 2
.na
Default value: \fB2\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_abd_scatter_min_size\fR (uint)
+.ad
+.RS 12n
+This is the minimum allocation size that will use scatter (page-based)
+ABD's. Smaller allocations will use linear ABD's.
+.sp
+Default value: \fB1536\fR (512B and 1KB allocations will be linear).
+.RE
+
.sp
.ne 2
.na
.RS 12n
When the number of bytes consumed by dnodes in the ARC exceeds this number of
bytes, try to unpin some of it in response to demand for non-metadata. This
-value acts as a floor to the amount of dnode metadata, and defaults to 0 which
+value acts as a ceiling to the amount of dnode metadata, and defaults to 0 which
indicates that a percent which is based on \fBzfs_arc_dnode_limit_percent\fR of
the ARC meta buffers that may be used for dnodes.
See also \fBzfs_arc_dnode_limit\fR which serves a similar purpose but has a
higher priority if set to nonzero value.
.sp
-Default value: \fB10\fR.
+Default value: \fB10\fR%.
.RE
.sp
.ad
.RS 12n
Percentage of ARC dnodes to try to scan in response to demand for non-metadata
-when the number of bytes consumed by dnodes exceeds \fBzfs_arc_dnode_limit\fB.
+when the number of bytes consumed by dnodes exceeds \fBzfs_arc_dnode_limit\fR.
.sp
-Default value: \fB10% of the number of dnodes in the ARC\fR.
+Default value: \fB10\fR% of the number of dnodes in the ARC.
.RE
.sp
\fBzfs_arc_grow_retry\fR (int)
.ad
.RS 12n
-After a memory pressure event the ARC will wait this many seconds before trying
-to resume growth
+If set to a non zero value, it will replace the arc_grow_retry value with this value.
+The arc_grow_retry value (default 5) is the number of seconds the ARC will wait before
+trying to resume growth after a memory pressure event.
.sp
-Default value: \fB5\fR.
+Default value: \fB0\fR.
.RE
.sp
Throttle I/O when free system memory drops below this percentage of total
system memory. Setting this value to 0 will disable the throttle.
.sp
-Default value: \fB10\fR.
+Default value: \fB10\fR%.
.RE
.sp
Default value: \fB0\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_arc_meta_adjust_restarts\fR (ulong)
+.ad
+.RS 12n
+The number of restart passes to make while scanning the ARC attempting
+the free buffers in order to stay below the \fBzfs_arc_meta_limit\fR.
+This value should not need to be tuned but is available to facilitate
+performance analysis.
+.sp
+Default value: \fB4096\fR.
+.RE
+
.sp
.ne 2
.na
higher priority if set to nonzero value.
.sp
-Default value: \fB75\fR.
+Default value: \fB75\fR%.
.RE
.sp
.sp
.ne 2
.na
-\fBzfs_arc_meta_adjust_restarts\fR (ulong)
+\fBzfs_arc_meta_strategy\fR (int)
.ad
.RS 12n
-The number of restart passes to make while scanning the ARC attempting
-the free buffers in order to stay below the \fBzfs_arc_meta_limit\fR.
-This value should not need to be tuned but is available to facilitate
-performance analysis.
+Define the strategy for ARC meta data buffer eviction (meta reclaim strategy).
+A value of 0 (META_ONLY) will evict only the ARC meta data buffers.
+A value of 1 (BALANCED) indicates that additional data buffers may be evicted if
+that is required to in order to evict the required number of meta data buffers.
.sp
-Default value: \fB4096\fR.
+Default value: \fB1\fR.
.RE
.sp
\fBzfs_arc_min\fR (ulong)
.ad
.RS 12n
-Min arc size
+Min arc size of ARC in bytes. If set to 0 then arc_c_min will default to
+consuming the larger of 32M or 1/32 of total system memory.
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_min_prefetch_ms\fR (int)
+.ad
+.RS 12n
+Minimum time prefetched blocks are locked in the ARC, specified in ms.
+A value of \fB0\fR will default to 1000 ms.
.sp
-Default value: \fB100\fR.
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_arc_min_prefetch_lifespan\fR (int)
+\fBzfs_arc_min_prescient_prefetch_ms\fR (int)
.ad
.RS 12n
-Minimum time prefetched blocks are locked in the ARC, specified in jiffies.
-A value of 0 will default to 1 second.
+Minimum time "prescient prefetched" blocks are locked in the ARC, specified
+in ms. These blocks are meant to be prefetched fairly aggresively ahead of
+the code that may use them. A value of \fB0\fR will default to 6000 ms.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_arc_num_sublists_per_state\fR (int)
+\fBzfs_max_missing_tvds\fR (int)
+.ad
+.RS 12n
+Number of missing top-level vdevs which will be allowed during
+pool import (only in read-only mode).
+.sp
+Default value: \fB0\fR
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_multilist_num_sublists\fR (int)
.ad
.RS 12n
To allow more fine-grained locking, each ARC state contains a series
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.
+sub-lists per ARC state, and also applies to other uses of the
+multilist data structure.
.sp
-Default value: \fR1\fB or the number of online CPUs, whichever is greater
+Default value: \fB4\fR or the number of online CPUs, whichever is greater
.RE
.sp
\fBzfs_arc_p_min_shift\fR (int)
.ad
.RS 12n
-arc_c shift to calc min/max arc_p
+If set to a non zero value, this will update arc_p_min_shift (default 4)
+with the new value.
+arc_p_min_shift is used to shift of arc_c for calculating both min and max
+max arc_p
.sp
-Default value: \fB4\fR.
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_arc_p_aggressive_disable\fR (int)
+\fBzfs_arc_p_dampener_disable\fR (int)
.ad
.RS 12n
-Disable aggressive arc_p growth
+Disable arc_p adapt dampener
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
.sp
.ne 2
.na
-\fBzfs_arc_p_dampener_disable\fR (int)
+\fBzfs_arc_shrink_shift\fR (int)
.ad
.RS 12n
-Disable arc_p adapt dampener
+If set to a non zero value, this will update arc_shrink_shift (default 7)
+with the new value.
.sp
-Use \fB1\fR for yes (default) and \fB0\fR to disable.
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_arc_shrink_shift\fR (int)
+\fBzfs_arc_pc_percent\fR (uint)
.ad
.RS 12n
-log2(fraction of arc to reclaim)
+Percent of pagecache to reclaim arc to
+
+This tunable allows ZFS arc to play more nicely with the kernel's LRU
+pagecache. It can guarantee that the arc size won't collapse under scanning
+pressure on the pagecache, yet still allows arc to be reclaimed down to
+zfs_arc_min if necessary. This value is specified as percent of pagecache
+size (as measured by NR_FILE_PAGES) where that percent may exceed 100. This
+only operates during memory pressure/reclaim.
.sp
-Default value: \fB5\fR.
+Default value: \fB0\fR% (disabled).
.RE
.sp
.sp
.ne 2
.na
-\fBzfs_dbgmsg_enable\fR (int)
+\fBzfs_checksums_per_second\fR (int)
.ad
.RS 12n
-Internally ZFS keeps a small log to facilitate debugging. By default the log
-is disabled, to enable it set this option to 1. The contents of the log can
-be accessed by reading the /proc/spl/kstat/zfs/dbgmsg file. Writing 0 to
-this proc file clears the log.
+Rate limit checksum events to this many per second. Note that this should
+not be set below the zed thresholds (currently 10 checksums over 10 sec)
+or else zed may not trigger any action.
.sp
-Default value: \fB0\fR.
+Default value: 20
.RE
.sp
.ne 2
.na
-\fBzfs_dbgmsg_maxsize\fR (int)
+\fBzfs_commit_timeout_pct\fR (int)
.ad
.RS 12n
-The maximum size in bytes of the internal ZFS debug log.
+This controls the amount of time that a ZIL block (lwb) will remain "open"
+when it isn't "full", and it has a thread waiting for it to be committed to
+stable storage. The timeout is scaled based on a percentage of the last lwb
+latency to avoid significantly impacting the latency of each individual
+transaction record (itx).
.sp
-Default value: \fB4M\fR.
+Default value: \fB5\fR%.
.RE
.sp
.ne 2
.na
-\fBzfs_dbuf_state_index\fR (int)
+\fBzfs_condense_indirect_vdevs_enable\fR (int)
.ad
.RS 12n
-This feature is currently unused. It is normally used for controlling what
-reporting is available under /proc/spl/kstat/zfs.
+Enable condensing indirect vdev mappings. When set to a non-zero value,
+attempt to condense indirect vdev mappings if the mapping uses more than
+\fBzfs_condense_min_mapping_bytes\fR bytes of memory and if the obsolete
+space map object uses more than \fBzfs_condense_max_obsolete_bytes\fR
+bytes on-disk. The condensing process is an attempt to save memory by
+removing obsolete mappings.
.sp
-Default value: \fB0\fR.
+Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_deadman_enabled\fR (int)
+\fBzfs_condense_max_obsolete_bytes\fR (ulong)
.ad
.RS 12n
-Enable deadman timer. See description below.
+Only attempt to condense indirect vdev mappings if the on-disk size
+of the obsolete space map object is greater than this number of bytes
+(see \fBfBzfs_condense_indirect_vdevs_enable\fR).
.sp
-Use \fB1\fR for yes (default) and \fB0\fR to disable.
+Default value: \fB1,073,741,824\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_deadman_synctime_ms\fR (ulong)
+\fBzfs_condense_min_mapping_bytes\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.
+Minimum size vdev mapping to attempt to condense (see
+\fBzfs_condense_indirect_vdevs_enable\fR).
.sp
-Default value: \fB1,000,000\fR.
+Default value: \fB131,072\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_dedup_prefetch\fR (int)
+\fBzfs_dbgmsg_enable\fR (int)
.ad
.RS 12n
-Enable prefetching dedup-ed blks
+Internally ZFS keeps a small log to facilitate debugging. By default the log
+is disabled, to enable it set this option to 1. The contents of the log can
+be accessed by reading the /proc/spl/kstat/zfs/dbgmsg file. Writing 0 to
+this proc file clears the log.
.sp
-Use \fB1\fR for yes and \fB0\fR to disable (default).
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_delay_min_dirty_percent\fR (int)
+\fBzfs_dbgmsg_maxsize\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".
+The maximum size in bytes of the internal ZFS debug log.
.sp
-Default value: \fB60\fR.
+Default value: \fB4M\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_delay_scale\fR (int)
+\fBzfs_dbuf_state_index\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
-For the smoothest delay, this value should be about 1 billion divided
-by the maximum number of operations per second. This will smoothly
-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.
+This feature is currently unused. It is normally used for controlling what
+reporting is available under /proc/spl/kstat/zfs.
.sp
-Default value: \fB500,000\fR.
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_delete_blocks\fR (ulong)
+\fBzfs_deadman_enabled\fR (int)
.ad
.RS 12n
-This is the used to define a large file for the purposes of delete. Files
-containing more than \fBzfs_delete_blocks\fR will be deleted asynchronously
-while smaller files are deleted synchronously. Decreasing this value will
-reduce the time spent in an unlink(2) system call at the expense of a longer
-delay before the freed space is available.
+When a pool sync operation takes longer than \fBzfs_deadman_synctime_ms\fR
+milliseconds, or when an individual I/O takes longer than
+\fBzfs_deadman_ziotime_ms\fR milliseconds, then the operation is considered to
+be "hung". If \fBzfs_deadman_enabled\fR is set then the deadman behavior is
+invoked as described by the \fBzfs_deadman_failmode\fR module option.
+By default the deadman is enabled and configured to \fBwait\fR which results
+in "hung" I/Os only being logged. The deadman is automatically disabled
+when a pool gets suspended.
.sp
-Default value: \fB20,480\fR.
+Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_dirty_data_max\fR (int)
+\fBzfs_deadman_failmode\fR (charp)
.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".
+Controls the failure behavior when the deadman detects a "hung" I/O. Valid
+values are \fBwait\fR, \fBcontinue\fR, and \fBpanic\fR.
+.sp
+\fBwait\fR - Wait for a "hung" I/O to complete. For each "hung" I/O a
+"deadman" event will be posted describing that I/O.
.sp
-Default value: 10 percent of all memory, capped at \fBzfs_dirty_data_max_max\fR.
+\fBcontinue\fR - Attempt to recover from a "hung" I/O by re-dispatching it
+to the I/O pipeline if possible.
+.sp
+\fBpanic\fR - Panic the system. This can be used to facilitate an automatic
+fail-over to a properly configured fail-over partner.
+.sp
+Default value: \fBwait\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_dirty_data_max_max\fR (int)
+\fBzfs_deadman_checktime_ms\fR (int)
.ad
.RS 12n
-Maximum allowable value of \fBzfs_dirty_data_max\fR, expressed in bytes.
+Check time in milliseconds. This defines the frequency at which we check
+for hung I/O and potentially invoke the \fBzfs_deadman_failmode\fR behavior.
+.sp
+Default value: \fB60,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_deadman_synctime_ms\fR (ulong)
+.ad
+.RS 12n
+Interval in milliseconds after which the deadman is triggered and also
+the interval after which a pool sync operation is considered to be "hung".
+Once this limit is exceeded the deadman will be invoked every
+\fBzfs_deadman_checktime_ms\fR milliseconds until the pool sync completes.
+.sp
+Default value: \fB600,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_deadman_ziotime_ms\fR (ulong)
+.ad
+.RS 12n
+Interval in milliseconds after which the deadman is triggered and an
+individual I/O operation is considered to be "hung". As long as the I/O
+remains "hung" the deadman will be invoked every \fBzfs_deadman_checktime_ms\fR
+milliseconds until the I/O completes.
+.sp
+Default value: \fB300,000\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 and \fB0\fR to disable (default).
+.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
+For the smoothest delay, this value should be about 1 billion divided
+by the maximum number of operations per second. This will smoothly
+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
+\fBzfs_slow_io_events_per_second\fR (int)
+.ad
+.RS 12n
+Rate limit delay zevents (which report slow I/Os) to this many per second.
+.sp
+Default value: 20
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_unlink_suspend_progress\fR (uint)
+.ad
+.RS 12n
+When enabled, files will not be asynchronously removed from the list of pending
+unlinks and the space they consume will be leaked. Once this option has been
+disabled and the dataset is remounted, the pending unlinks will be processed
+and the freed space returned to the pool.
+This option is used by the test suite to facilitate testing.
+.sp
+Uses \fB0\fR (default) to allow progress and \fB1\fR to pause progress.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_delete_blocks\fR (ulong)
+.ad
+.RS 12n
+This is the used to define a large file for the purposes of delete. Files
+containing more than \fBzfs_delete_blocks\fR will be deleted asynchronously
+while smaller files are deleted synchronously. Decreasing this value will
+reduce the time spent in an unlink(2) system call at the expense of a longer
+delay before the freed space is available.
+.sp
+Default value: \fB20,480\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\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: \fB10\fR% of physical RAM, 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
"ZFS TRANSACTION DELAY".
.sp
-Default value: 25% of physical RAM.
+Default value: \fB25\fR% of physical RAM.
.RE
.sp
The parameter \fBzfs_dirty_data_max_max\fR takes precedence over this
one. See the section "ZFS TRANSACTION DELAY".
.sp
-Default value: \fN25\fR.
+Default value: \fB25\fR%.
.RE
.sp
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.
+Default value: \fB10\fR%, subject to \fBzfs_dirty_data_max_max\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_dirty_data_sync\fR (int)
+\fBzfs_dirty_data_sync_percent\fR (int)
.ad
.RS 12n
-Start syncing out a transaction group if there is at least this much dirty data.
+Start syncing out a transaction group if there's at least this much dirty data
+as a percentage of \fBzfs_dirty_data_max\fR. This should be less than
+\fBzfs_vdev_async_write_active_min_dirty_percent\fR.
.sp
-Default value: \fB67,108,864\fR.
+Default value: \fB20\fR% of \fBzfs_dirty_data_max\fR.
.RE
.sp
Select a fletcher 4 implementation.
.sp
Supported selectors are: \fBfastest\fR, \fBscalar\fR, \fBsse2\fR, \fBssse3\fR,
-\fBavx2\fR, and \fBavx512f\fR.
+\fBavx2\fR, \fBavx512f\fR, and \fBaarch64_neon\fR.
All of the selectors except \fBfastest\fR and \fBscalar\fR require instruction
set extensions to be available and will only appear if ZFS detects that they are
present at runtime. If multiple implementations of fletcher 4 are available,
.sp
.ne 2
.na
-\fBzfs_free_max_blocks\fR (ulong)
+\fBzfs_async_block_max_blocks\fR (ulong)
.ad
.RS 12n
Maximum number of blocks freed in a single txg.
Default value: \fB100,000\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_override_estimate_recordsize\fR (ulong)
+.ad
+.RS 12n
+Record size calculation override for zfs send estimates.
+.sp
+Default value: \fB0\fR.
+.RE
+
.sp
.ne 2
.na
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.
+Default value: \fB60\fR%.
.RE
.sp
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.
+Default value: \fB30\fR%.
.RE
.sp
Minimum asynchronous write I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
+Lower values are associated with better latency on rotational media but poorer
+resilver performance. The default value of 2 was chosen as a compromise. A
+value of 3 has been shown to improve resilver performance further at a cost of
+further increasing latency.
+.sp
+Default value: \fB2\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_initializing_max_active\fR (int)
+.ad
+.RS 12n
+Maximum initializing 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_initializing_min_active\fR (int)
+.ad
+.RS 12n
+Minimum initializing I/Os active to each device.
+See the section "ZFS I/O SCHEDULER".
+.sp
Default value: \fB1\fR.
.RE
Default value: \fB1,000\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_vdev_removal_max_active\fR (int)
+.ad
+.RS 12n
+Maximum removal 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_removal_min_active\fR (int)
+.ad
+.RS 12n
+Minimum removal I/Os active to each device.
+See the section "ZFS I/O SCHEDULER".
+.sp
+Default value: \fB1\fR.
+.RE
+
.sp
.ne 2
.na
.sp
.ne 2
.na
-\fBzfs_vdev_queue_depth_pct\fR (int)
+\fBzfs_vdev_trim_max_active\fR (int)
.ad
.RS 12n
-The queue depth percentage for each top-level virtual device.
-Used in conjunction with zfs_vdev_async_max_active.
+Maximum trim/discard I/Os active to each device.
+See the section "ZFS I/O SCHEDULER".
.sp
-Default value: \fB1000\fR.
+Default value: \fB2\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_disable_dup_eviction\fR (int)
+\fBzfs_vdev_trim_min_active\fR (int)
.ad
.RS 12n
-Disable duplicate buffer eviction
+Minimum trim/discard I/Os active to each device.
+See the section "ZFS I/O SCHEDULER".
.sp
-Use \fB1\fR for yes and \fB0\fR for no (default).
+Default value: \fB1\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_queue_depth_pct\fR (int)
+.ad
+.RS 12n
+Maximum number of queued allocations per top-level vdev expressed as
+a percentage of \fBzfs_vdev_async_write_max_active\fR which allows the
+system to detect devices that are more capable of handling allocations
+and to allocate more blocks to those devices. It allows for dynamic
+allocation distribution when devices are imbalanced as fuller devices
+will tend to be slower than empty devices.
+
+See also \fBzio_dva_throttle_enabled\fR.
+.sp
+Default value: \fB1000\fR%.
.RE
.sp
16 ZFS_DEBUG_MODIFY
Check for illegally modified ARC buffers.
_
-32 ZFS_DEBUG_SPA
- Enable spa_dbgmsg entries in the debug log.
-_
64 ZFS_DEBUG_ZIO_FREE
Enable verification of block frees.
_
128 ZFS_DEBUG_HISTOGRAM_VERIFY
Enable extra spacemap histogram verifications.
+_
+256 ZFS_DEBUG_METASLAB_VERIFY
+ Verify space accounting on disk matches in-core range_trees.
+_
+512 ZFS_DEBUG_SET_ERROR
+ Enable SET_ERROR and dprintf entries in the debug log.
+_
+1024 ZFS_DEBUG_INDIRECT_REMAP
+ Verify split blocks created by device removal.
+_
+2048 ZFS_DEBUG_TRIM
+ Verify TRIM ranges are always within the allocatable range tree.
.TE
.sp
* Requires debug build.
approach of not setting it, so that there is no possibility of
leaking space in the "partial temporary" failure case.
.sp
-Default value: \fB0\fR.
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_free_min_time_ms\fR (int)
+.ad
+.RS 12n
+During a \fBzfs destroy\fR operation using \fBfeature@async_destroy\fR a minimum
+of this much time will be spent working on freeing blocks 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. Larger blocks will be treated as if the
+dataset being written to had the property setting \fBlogbias=throughput\fR.
+.sp
+Default value: \fB32,768\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_initialize_value\fR (ulong)
+.ad
+.RS 12n
+Pattern written to vdev free space by \fBzpool initialize\fR.
+.sp
+Default value: \fB16,045,690,984,833,335,022\fR (0xdeadbeefdeadbeee).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_lua_max_instrlimit\fR (ulong)
+.ad
+.RS 12n
+The maximum execution time limit that can be set for a ZFS channel program,
+specified as a number of Lua instructions.
+.sp
+Default value: \fB100,000,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_lua_max_memlimit\fR (ulong)
+.ad
+.RS 12n
+The maximum memory limit that can be set for a ZFS channel program, specified
+in bytes.
+.sp
+Default value: \fB104,857,600\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_max_dataset_nesting\fR (int)
+.ad
+.RS 12n
+The maximum depth of nested datasets. This value can be tuned temporarily to
+fix existing datasets that exceed the predefined limit.
+.sp
+Default value: \fB50\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_max_recordsize\fR (int)
+.ad
+.RS 12n
+We currently support block sizes from 512 bytes to 16MB. The benefits of
+larger blocks, and thus larger I/O, need to be weighed against the cost of
+COWing a giant block to modify one byte. Additionally, very large blocks
+can have an impact on i/o latency, and also potentially on the memory
+allocator. Therefore, we do not allow the recordsize to be set larger than
+zfs_max_recordsize (default 1MB). Larger blocks can be created by changing
+this tunable, and pools with larger blocks can always be imported and used,
+regardless of this setting.
+.sp
+Default value: \fB1,048,576\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_metaslab_fragmentation_threshold\fR (int)
+.ad
+.RS 12n
+Allow metaslabs to keep their active state as long as their fragmentation
+percentage is less than or equal to this value. An active metaslab that
+exceeds this threshold will no longer keep its active status allowing
+better metaslabs to be selected.
+.sp
+Default value: \fB70\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_mg_fragmentation_threshold\fR (int)
+.ad
+.RS 12n
+Metaslab groups are considered eligible for allocations if their
+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.
+.sp
+Default value: \fB85\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_mg_noalloc_threshold\fR (int)
+.ad
+.RS 12n
+Defines a threshold at which metaslab groups should be eligible for
+allocations. The value is expressed as a percentage of free space
+beyond which a metaslab group is always eligible for allocations.
+If a metaslab group's free space is less than or equal to the
+threshold, the allocator will avoid allocating to that group
+unless all groups in the pool have reached the threshold. Once all
+groups have reached the threshold, all groups are allowed to accept
+allocations. The default value of 0 disables the feature and causes
+all metaslab groups to be eligible for allocations.
+
+This parameter allows one to deal with pools having heavily imbalanced
+vdevs such as would be the case when a new vdev has been added.
+Setting the threshold to a non-zero percentage will stop allocations
+from being made to vdevs that aren't filled to the specified percentage
+and allow lesser filled vdevs to acquire more allocations than they
+otherwise would under the old \fBzfs_mg_alloc_failures\fR facility.
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_ddt_data_is_special\fR (int)
+.ad
+.RS 12n
+If enabled, ZFS will place DDT data into the special allocation class.
+.sp
+Default value: \fB1\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_user_indirect_is_special\fR (int)
+.ad
+.RS 12n
+If enabled, ZFS will place user data (both file and zvol) indirect blocks
+into the special allocation class.
+.sp
+Default value: \fB1\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_multihost_history\fR (int)
+.ad
+.RS 12n
+Historical statistics for the last N multihost updates will be available in
+\fB/proc/spl/kstat/zfs/<pool>/multihost\fR
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_multihost_interval\fR (ulong)
+.ad
+.RS 12n
+Used to control the frequency of multihost writes which are performed when the
+\fBmultihost\fR pool property is on. This is one factor used to determine the
+length of the activity check during import.
+.sp
+The multihost write period is \fBzfs_multihost_interval / leaf-vdevs\fR
+milliseconds. On average a multihost write will be issued for each leaf vdev
+every \fBzfs_multihost_interval\fR milliseconds. In practice, the observed
+period can vary with the I/O load and this observed value is the delay which is
+stored in the uberblock.
+.sp
+Default value: \fB1000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_multihost_import_intervals\fR (uint)
+.ad
+.RS 12n
+Used to control the duration of the activity test on import. Smaller values of
+\fBzfs_multihost_import_intervals\fR will reduce the import time but increase
+the risk of failing to detect an active pool. The total activity check time is
+never allowed to drop below one second.
+.sp
+On import the activity check waits a minimum amount of time determined by
+\fBzfs_multihost_interval * zfs_multihost_import_intervals\fR, or the same
+product computed on the host which last had the pool imported (whichever is
+greater). The activity check time may be further extended if the value of mmp
+delay found in the best uberblock indicates actual multihost updates happened
+at longer intervals than \fBzfs_multihost_interval\fR. A minimum value of
+\fB100ms\fR is enforced.
+.sp
+A value of 0 is ignored and treated as if it was set to 1.
+.sp
+Default value: \fB20\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_multihost_fail_intervals\fR (uint)
+.ad
+.RS 12n
+Controls the behavior of the pool when multihost write failures or delays are
+detected.
+.sp
+When \fBzfs_multihost_fail_intervals = 0\fR, multihost write failures or delays
+are ignored. The failures will still be reported to the ZED which depending on
+its configuration may take action such as suspending the pool or offlining a
+device.
+
+.sp
+When \fBzfs_multihost_fail_intervals > 0\fR, the pool will be suspended if
+\fBzfs_multihost_fail_intervals * zfs_multihost_interval\fR milliseconds pass
+without a successful mmp write. This guarantees the activity test will see
+mmp writes if the pool is imported. A value of 1 is ignored and treated as
+if it was set to 2. This is necessary to prevent the pool from being suspended
+due to normal, small I/O latency variations.
+
+.sp
+Default value: \fB10\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_no_scrub_io\fR (int)
+.ad
+.RS 12n
+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
+
+.sp
+.ne 2
+.na
+\fBzfs_no_scrub_prefetch\fR (int)
+.ad
+.RS 12n
+Set to disable block prefetching for scrubs.
+.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 flush operations on disks when writing. Setting this will
+cause pool corruption on power loss if a volatile out-of-order write cache
+is enabled.
+.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_dmu_offset_next_sync\fR (int)
+.ad
+.RS 12n
+Enable forcing txg sync to find holes. When enabled forces ZFS to act
+like prior versions when SEEK_HOLE or SEEK_DATA flags are used, which
+when a dnode is dirty causes txg's to be synced so that this data can be
+found.
+.sp
+Use \fB1\fR for yes and \fB0\fR to disable (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_pd_bytes_max\fR (int)
+.ad
+.RS 12n
+The number of bytes which should be prefetched during a pool traversal
+(eg: \fBzfs send\fR or other data crawling operations)
+.sp
+Default value: \fB52,428,800\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_per_txg_dirty_frees_percent \fR (ulong)
+.ad
+.RS 12n
+Tunable to control percentage of dirtied indirect blocks from frees allowed
+into one TXG. After this threshold is crossed, additional frees will wait until
+the next TXG.
+A value of zero will disable this throttle.
+.sp
+Default value: \fB5\fR, set to \fB0\fR to disable.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_prefetch_disable\fR (int)
+.ad
+.RS 12n
+This tunable disables predictive prefetch. Note that it leaves "prescient"
+prefetch (e.g. prefetch for zfs send) intact. Unlike predictive prefetch,
+prescient prefetch never issues i/os that end up not being needed, so it
+can't hurt performance.
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_qat_checksum_disable\fR (int)
+.ad
+.RS 12n
+This tunable disables qat hardware acceleration for sha256 checksums. It
+may be set after the zfs modules have been loaded to initialize the qat
+hardware as long as support is compiled in and the qat driver is present.
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_qat_compress_disable\fR (int)
+.ad
+.RS 12n
+This tunable disables qat hardware acceleration for gzip compression. It
+may be set after the zfs modules have been loaded to initialize the qat
+hardware as long as support is compiled in and the qat driver is present.
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_qat_encrypt_disable\fR (int)
+.ad
+.RS 12n
+This tunable disables qat hardware acceleration for AES-GCM encryption. It
+may be set after the zfs modules have been loaded to initialize the qat
+hardware as long as support is compiled in and the qat driver is present.
+.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_free_min_time_ms\fR (int)
+\fBzfs_read_history\fR (int)
.ad
.RS 12n
-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.
+Historical statistics for the last N reads will be available in
+\fB/proc/spl/kstat/zfs/<pool>/reads\fR
.sp
-Default value: \fB1,000\fR.
+Default value: \fB0\fR (no data is kept).
.RE
.sp
.ne 2
.na
-\fBzfs_immediate_write_sz\fR (long)
+\fBzfs_read_history_hits\fR (int)
.ad
.RS 12n
-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.
+Include cache hits in read history
.sp
-Default value: \fB32,768\fR.
+Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
-\fBzfs_max_recordsize\fR (int)
+\fBzfs_reconstruct_indirect_combinations_max\fR (int)
.ad
-.RS 12n
-We currently support block sizes from 512 bytes to 16MB. The benefits of
-larger blocks, and thus larger IO, need to be weighed against the cost of
-COWing a giant block to modify one byte. Additionally, very large blocks
-can have an impact on i/o latency, and also potentially on the memory
-allocator. Therefore, we do not allow the recordsize to be set larger than
-zfs_max_recordsize (default 1MB). Larger blocks can be created by changing
-this tunable, and pools with larger blocks can always be imported and used,
-regardless of this setting.
+.RS 12na
+If an indirect split block contains more than this many possible unique
+combinations when being reconstructed, consider it too computationally
+expensive to check them all. Instead, try at most
+\fBzfs_reconstruct_indirect_combinations_max\fR randomly-selected
+combinations each time the block is accessed. This allows all segment
+copies to participate fairly in the reconstruction when all combinations
+cannot be checked and prevents repeated use of one bad copy.
.sp
-Default value: \fB1,048,576\fR.
+Default value: \fB4096\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_mdcomp_disable\fR (int)
+\fBzfs_recover\fR (int)
.ad
.RS 12n
-Disable meta data compression
+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_metaslab_fragmentation_threshold\fR (int)
+\fBzfs_removal_ignore_errors\fR (int)
.ad
.RS 12n
-Allow metaslabs to keep their active state as long as their fragmentation
-percentage is less than or equal to this value. An active metaslab that
-exceeds this threshold will no longer keep its active status allowing
-better metaslabs to be selected.
.sp
-Default value: \fB70\fR.
+Ignore hard IO errors during device removal. When set, if a device encounters
+a hard IO error during the removal process the removal will not be cancelled.
+This can result in a normally recoverable block becoming permanently damaged
+and is not recommended. This should only be used as a last resort when the
+pool cannot be returned to a healthy state prior to removing the device.
+.sp
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_mg_fragmentation_threshold\fR (int)
+\fBzfs_resilver_min_time_ms\fR (int)
.ad
.RS 12n
-Metaslab groups are considered eligible for allocations if their
-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.
+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: \fB85\fR.
+Default value: \fB3,000\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_mg_noalloc_threshold\fR (int)
+\fBzfs_scan_ignore_errors\fR (int)
.ad
.RS 12n
-Defines a threshold at which metaslab groups should be eligible for
-allocations. The value is expressed as a percentage of free space
-beyond which a metaslab group is always eligible for allocations.
-If a metaslab group's free space is less than or equal to the
-threshold, the allocator will avoid allocating to that group
-unless all groups in the pool have reached the threshold. Once all
-groups have reached the threshold, all groups are allowed to accept
-allocations. The default value of 0 disables the feature and causes
-all metaslab groups to be eligible for allocations.
-
-This parameter allows to deal with pools having heavily imbalanced
-vdevs such as would be the case when a new vdev has been added.
-Setting the threshold to a non-zero percentage will stop allocations
-from being made to vdevs that aren't filled to the specified percentage
-and allow lesser filled vdevs to acquire more allocations than they
-otherwise would under the old \fBzfs_mg_alloc_failures\fR facility.
+If set to a nonzero value, remove the DTL (dirty time list) upon
+completion of a pool scan (scrub) even if there were unrepairable
+errors. It is intended to be used during pool repair or recovery to
+stop resilvering when the pool is next imported.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_no_scrub_io\fR (int)
+\fBzfs_scrub_min_time_ms\fR (int)
.ad
.RS 12n
-Set for no scrub I/O. This results in scrubs not actually scrubbing data and
-simply doing a metadata crawl of the pool instead.
+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
-Use \fB1\fR for yes and \fB0\fR for no (default).
+Default value: \fB1,000\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_no_scrub_prefetch\fR (int)
+\fBzfs_scan_checkpoint_intval\fR (int)
.ad
.RS 12n
-Set to disable block prefetching for scrubs.
+To preserve progress across reboots the sequential scan algorithm periodically
+needs to stop metadata scanning and issue all the verifications I/Os to disk.
+The frequency of this flushing is determined by the
+\fBzfs_scan_checkpoint_intval\fR tunable.
.sp
-Use \fB1\fR for yes and \fB0\fR for no (default).
+Default value: \fB7200\fR seconds (every 2 hours).
.RE
.sp
.ne 2
.na
-\fBzfs_nocacheflush\fR (int)
+\fBzfs_scan_fill_weight\fR (int)
.ad
.RS 12n
-Disable cache flush operations on disks when writing. Beware, this may cause
-corruption if disks re-order writes.
+This tunable affects how scrub and resilver I/O segments are ordered. A higher
+number indicates that we care more about how filled in a segment is, while a
+lower number indicates we care more about the size of the extent without
+considering the gaps within a segment. This value is only tunable upon module
+insertion. Changing the value afterwards will have no affect on scrub or
+resilver performance.
.sp
-Use \fB1\fR for yes and \fB0\fR for no (default).
+Default value: \fB3\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_nopwrite_enabled\fR (int)
+\fBzfs_scan_issue_strategy\fR (int)
.ad
.RS 12n
-Enable NOP writes
+Determines the order that data will be verified while scrubbing or resilvering.
+If set to \fB1\fR, data will be verified as sequentially as possible, given the
+amount of memory reserved for scrubbing (see \fBzfs_scan_mem_lim_fact\fR). This
+may improve scrub performance if the pool's data is very fragmented. If set to
+\fB2\fR, the largest mostly-contiguous chunk of found data will be verified
+first. By deferring scrubbing of small segments, we may later find adjacent data
+to coalesce and increase the segment size. If set to \fB0\fR, zfs will use
+strategy \fB1\fR during normal verification and strategy \fB2\fR while taking a
+checkpoint.
.sp
-Use \fB1\fR for yes (default) and \fB0\fR to disable.
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_pd_bytes_max\fR (int)
+\fBzfs_scan_legacy\fR (int)
.ad
.RS 12n
-The number of bytes which should be prefetched during a pool traversal
-(eg: \fRzfs send\fB or other data crawling operations)
+A value of 0 indicates that scrubs and resilvers will gather metadata in
+memory before issuing sequential I/O. A value of 1 indicates that the legacy
+algorithm will be used where I/O is initiated as soon as it is discovered.
+Changing this value to 0 will not affect scrubs or resilvers that are already
+in progress.
.sp
-Default value: \fB52,428,800\fR.
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_prefetch_disable\fR (int)
+\fBzfs_scan_max_ext_gap\fR (int)
.ad
.RS 12n
-This tunable disables predictive prefetch. Note that it leaves "prescient"
-prefetch (e.g. prefetch for zfs send) intact. Unlike predictive prefetch,
-prescient prefetch never issues i/os that end up not being needed, so it
-can't hurt performance.
+Indicates the largest gap in bytes between scrub / resilver I/Os that will still
+be considered sequential for sorting purposes. Changing this value will not
+affect scrubs or resilvers that are already in progress.
.sp
-Use \fB1\fR for yes and \fB0\fR for no (default).
+Default value: \fB2097152 (2 MB)\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_read_chunk_size\fR (long)
+\fBzfs_scan_mem_lim_fact\fR (int)
.ad
.RS 12n
-Bytes to read per chunk
+Maximum fraction of RAM used for I/O sorting by sequential scan algorithm.
+This tunable determines the hard limit for I/O sorting memory usage.
+When the hard limit is reached we stop scanning metadata and start issuing
+data verification I/O. This is done until we get below the soft limit.
.sp
-Default value: \fB1,048,576\fR.
+Default value: \fB20\fR which is 5% of RAM (1/20).
.RE
.sp
.ne 2
.na
-\fBzfs_read_history\fR (int)
+\fBzfs_scan_mem_lim_soft_fact\fR (int)
.ad
.RS 12n
-Historic statistics for the last N reads will be available in
-\fR/proc/spl/kstat/zfs/POOLNAME/reads\fB
+The fraction of the hard limit used to determined the soft limit for I/O sorting
+by the sequential scan algorithm. When we cross this limit from bellow no action
+is taken. When we cross this limit from above it is because we are issuing
+verification I/O. In this case (unless the metadata scan is done) we stop
+issuing verification I/O and start scanning metadata again until we get to the
+hard limit.
.sp
-Default value: \fB0\fR (no data is kept).
+Default value: \fB20\fR which is 5% of the hard limit (1/20).
.RE
.sp
.ne 2
.na
-\fBzfs_read_history_hits\fR (int)
+\fBzfs_scan_vdev_limit\fR (int)
.ad
.RS 12n
-Include cache hits in read history
+Maximum amount of data that can be concurrently issued at once for scrubs and
+resilvers per leaf device, given in bytes.
.sp
-Use \fB1\fR for yes and \fB0\fR for no (default).
+Default value: \fB41943040\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_recover\fR (int)
+\fBzfs_send_corrupt_data\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.
+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
.sp
.ne 2
.na
-\fBzfs_resilver_delay\fR (int)
+\fBzfs_send_queue_length\fR (int)
+.ad
+.RS 12n
+The maximum number of bytes allowed in the \fBzfs send\fR queue. This value
+must be at least twice the maximum block size in use.
+.sp
+Default value: \fB16,777,216\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_recv_queue_length\fR (int)
+.ad
+.RS 12n
+.sp
+The maximum number of bytes allowed in the \fBzfs receive\fR queue. This value
+must be at least twice the maximum block size in use.
+.sp
+Default value: \fB16,777,216\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_sync_pass_deferred_free\fR (int)
.ad
.RS 12n
-Number of ticks to delay prior to issuing a resilver I/O operation when
-a non-resilver or non-scrub I/O operation has occurred within the past
-\fBzfs_scan_idle\fR ticks.
+Flushing of data to disk is done in passes. Defer frees starting in this pass
.sp
Default value: \fB2\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_resilver_min_time_ms\fR (int)
+\fBzfs_spa_discard_memory_limit\fR (int)
.ad
.RS 12n
-Resilvers are processed by the sync thread. While resilvering it will spend
-at least this much time working on a resilver between txg flushes.
+Maximum memory used for prefetching a checkpoint's space map on each
+vdev while discarding the checkpoint.
.sp
-Default value: \fB3,000\fR.
+Default value: \fB16,777,216\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_scan_idle\fR (int)
+\fBzfs_sync_pass_dont_compress\fR (int)
.ad
.RS 12n
-Idle window in clock ticks. During a scrub or a resilver, if
-a non-scrub or non-resilver I/O operation has occurred during this
-window, the next scrub or resilver operation is delayed by, respectively
-\fBzfs_scrub_delay\fR or \fBzfs_resilver_delay\fR ticks.
+Don't compress starting in this pass
.sp
-Default value: \fB50\fR.
+Default value: \fB5\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_scan_min_time_ms\fR (int)
+\fBzfs_sync_pass_rewrite\fR (int)
.ad
.RS 12n
-Scrubs are processed by the sync thread. While scrubbing it will spend
-at least this much time working on a scrub between txg flushes.
+Rewrite new block pointers starting in this pass
.sp
-Default value: \fB1,000\fR.
+Default value: \fB2\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_scrub_delay\fR (int)
+\fBzfs_sync_taskq_batch_pct\fR (int)
.ad
.RS 12n
-Number of ticks to delay prior to issuing a scrub I/O operation when
-a non-scrub or non-resilver I/O operation has occurred within the past
-\fBzfs_scan_idle\fR ticks.
+This controls the number of threads used by the dp_sync_taskq. The default
+value of 75% will create a maximum of one thread per cpu.
.sp
-Default value: \fB4\fR.
+Default value: \fB75\fR%.
.RE
.sp
.ne 2
.na
-\fBzfs_send_corrupt_data\fR (int)
+\fBzfs_trim_extent_bytes_max\fR (unsigned int)
.ad
.RS 12n
-Allow sending of corrupt data (ignore read/checksum errors when sending data)
+Maximum size of TRIM command. Ranges larger than this will be split in to
+chunks no larger than \fBzfs_trim_extent_bytes_max\fR bytes before being
+issued to the device.
.sp
-Use \fB1\fR for yes and \fB0\fR for no (default).
+Default value: \fB134,217,728\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_sync_pass_deferred_free\fR (int)
+\fBzfs_trim_extent_bytes_min\fR (unsigned int)
.ad
.RS 12n
-Flushing of data to disk is done in passes. Defer frees starting in this pass
+Minimum size of TRIM commands. TRIM ranges smaller than this will be skipped
+unless they're part of a larger range which was broken in to chunks. This is
+done because it's common for these small TRIMs to negatively impact overall
+performance. This value can be set to 0 to TRIM all unallocated space.
.sp
-Default value: \fB2\fR.
+Default value: \fB32,768\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_sync_pass_dont_compress\fR (int)
+\fBzfs_trim_metaslab_skip\fR (unsigned int)
.ad
.RS 12n
-Don't compress starting in this pass
+Skip uninitialized metaslabs during the TRIM process. This option is useful
+for pools constructed from large thinly-provisioned devices where TRIM
+operations are slow. As a pool ages an increasing fraction of the pools
+metaslabs will be initialized progressively degrading the usefulness of
+this option. This setting is stored when starting a manual TRIM and will
+persist for the duration of the requested TRIM.
.sp
-Default value: \fB5\fR.
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_sync_pass_rewrite\fR (int)
+\fBzfs_trim_queue_limit\fR (unsigned int)
.ad
.RS 12n
-Rewrite new block pointers starting in this pass
+Maximum number of queued TRIMs outstanding per leaf vdev. The number of
+concurrent TRIM commands issued to the device is controlled by the
+\fBzfs_vdev_trim_min_active\fR and \fBzfs_vdev_trim_max_active\fR module
+options.
.sp
-Default value: \fB2\fR.
+Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_top_maxinflight\fR (int)
+\fBzfs_trim_txg_batch\fR (unsigned int)
.ad
.RS 12n
-Max concurrent I/Os per top-level vdev (mirrors or raidz arrays) allowed during
-scrub or resilver operations.
+The number of transaction groups worth of frees which should be aggregated
+before TRIM operations are issued to the device. This setting represents a
+trade-off between issuing larger, more efficient TRIM operations and the
+delay before the recently trimmed space is available for use by the device.
+.sp
+Increasing this value will allow frees to be aggregated for a longer time.
+This will result is larger TRIM operations and potentially increased memory
+usage. Decreasing this value will have the opposite effect. The default
+value of 32 was determined to be a reasonable compromise.
.sp
Default value: \fB32\fR.
.RE
\fBzfs_txg_history\fR (int)
.ad
.RS 12n
-Historic statistics for the last N txgs will be available in
-\fR/proc/spl/kstat/zfs/POOLNAME/txgs\fB
+Historical statistics for the last N txgs will be available in
+\fB/proc/spl/kstat/zfs/<pool>/txgs\fR
.sp
Default value: \fB0\fR.
.RE
Default value: \fB5\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_vdev_aggregate_trim\fR (int)
+.ad
+.RS 12n
+Allow TRIM I/Os to be aggregated. This is normally not helpful because
+the extents to be trimmed will have been already been aggregated by the
+metaslab. This option is provided for debugging and performance analysis.
+.sp
+Default value: \fB0\fR.
+.RE
+
.sp
.ne 2
.na
.RS 12n
Max vdev I/O aggregation size
.sp
+Default value: \fB1,048,576\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_aggregation_limit_non_rotating\fR (int)
+.ad
+.RS 12n
+Max vdev I/O aggregation size for non-rotating media
+.sp
Default value: \fB131,072\fR.
.RE
\fBzfs_vdev_cache_max\fR (int)
.ad
.RS 12n
-Inflate reads small than this value to meet the \fBzfs_vdev_cache_bshift\fR
-size.
+Inflate reads smaller than this value to meet the \fBzfs_vdev_cache_bshift\fR
+size (default 64k).
.sp
Default value: \fB16384\fR.
.RE
\fBzfs_vdev_scheduler\fR (charp)
.ad
.RS 12n
-Set the Linux I/O scheduler on whole disk vdevs to this scheduler
+Set the Linux I/O scheduler on whole disk vdevs to this scheduler. Valid options
+are noop, cfq, bfq & deadline
.sp
Default value: \fBnoop\fR.
.RE
sse2 - implementation using SSE2 instruction set (64bit x86 only)
ssse3 - implementation using SSSE3 instruction set (64bit x86 only)
avx2 - implementation using AVX2 instruction set (64bit x86 only)
+ avx512f - implementation using AVX512F instruction set (64bit x86 only)
+ avx512bw - implementation using AVX512F & AVX512BW instruction sets (64bit x86 only)
aarch64_neon - implementation using NEON (Aarch64/64 bit ARMv8 only)
aarch64_neonx2 - implementation using NEON with more unrolling (Aarch64/64 bit ARMv8 only)
.sp
Default value: \fB0\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_zil_clean_taskq_maxalloc\fR (int)
+.ad
+.RS 12n
+The maximum number of taskq entries that are allowed to be cached. When this
+limit is exceeded transaction records (itxs) will be cleaned synchronously.
+.sp
+Default value: \fB1048576\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_zil_clean_taskq_minalloc\fR (int)
+.ad
+.RS 12n
+The number of taskq entries that are pre-populated when the taskq is first
+created and are immediately available for use.
+.sp
+Default value: \fB1024\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_zil_clean_taskq_nthr_pct\fR (int)
+.ad
+.RS 12n
+This controls the number of threads used by the dp_zil_clean_taskq. The default
+value of 100% will create a maximum of one thread per cpu.
+.sp
+Default value: \fB100\fR%.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzil_nocacheflush\fR (int)
+.ad
+.RS 12n
+Disable the cache flush commands that are normally sent to the disk(s) by
+the ZIL after an LWB write has completed. Setting this will cause ZIL
+corruption on power loss if a volatile out-of-order write cache is enabled.
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
.sp
.ne 2
.na
.sp
.ne 2
.na
-\fBzil_slog_limit\fR (ulong)
+\fBzil_slog_bulk\fR (ulong)
.ad
.RS 12n
-Max commit bytes to separate log device
+Limit SLOG write size per commit executed with synchronous priority.
+Any writes above that will be executed with lower (asynchronous) priority
+to limit potential SLOG device abuse by single active ZIL writer.
.sp
-Default value: \fB1,048,576\fR.
+Default value: \fB786,432\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzio_deadman_log_all\fR (int)
+.ad
+.RS 12n
+If non-zero, the zio deadman will produce debugging messages (see
+\fBzfs_dbgmsg_enable\fR) for all zios, rather than only for leaf
+zios possessing a vdev. This is meant to be used by developers to gain
+diagnostic information for hang conditions which don't involve a mutex
+or other locking primitive; typically conditions in which a thread in
+the zio pipeline is looping indefinitely.
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzio_decompress_fail_fraction\fR (int)
+.ad
+.RS 12n
+If non-zero, this value represents the denominator of the probability that zfs
+should induce a decompression failure. For instance, for a 5% decompression
+failure rate, this value should be set to 20.
+.sp
+Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
-\fBzio_delay_max\fR (int)
+\fBzio_slow_io_ms\fR (int)
.ad
.RS 12n
-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.
+When an I/O operation takes more than \fBzio_slow_io_ms\fR milliseconds to
+complete is marked as a slow I/O. Each slow I/O causes a delay zevent. Slow
+I/O counters can be seen with "zpool status -s".
+
.sp
Default value: \fB30,000\fR.
.RE
\fBzio_dva_throttle_enabled\fR (int)
.ad
.RS 12n
-Throttle block allocations in the ZIO pipeline. This allows for
+Throttle block allocations in the I/O pipeline. This allows for
dynamic allocation distribution when devices are imbalanced.
+When enabled, the maximum number of pending allocations per top-level vdev
+is limited by \fBzfs_vdev_queue_depth_pct\fR.
.sp
Default value: \fB1\fR.
.RE
.ad
.RS 12n
Percentage of online CPUs (or CPU cores, etc) which will run a worker thread
-for IO. These workers are responsible for IO work such as compression and
+for I/O. These workers are responsible for I/O work such as compression and
checksum calculations. Fractional number of CPUs will be rounded down.
.sp
The default value of 75 was chosen to avoid using all CPUs which can result in
Default value: \fB131,072\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzvol_request_sync\fR (uint)
+.ad
+.RS 12n
+When processing I/O requests for a zvol submit them synchronously. This
+effectively limits the queue depth to 1 for each I/O submitter. When set
+to 0 requests are handled asynchronously by a thread pool. The number of
+requests which can be handled concurrently is controller by \fBzvol_threads\fR.
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzvol_threads\fR (uint)
+.ad
+.RS 12n
+Max number of threads which can handle zvol I/O requests concurrently.
+.sp
+Default value: \fB32\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzvol_volmode\fR (uint)
+.ad
+.RS 12n
+Defines zvol block devices behaviour when \fBvolmode\fR is set to \fBdefault\fR.
+Valid values are \fB1\fR (full), \fB2\fR (dev) and \fB3\fR (none).
+.sp
+Default value: \fB1\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
projects / mirror_zfs.git / blobdiff