Default value: \fB8,388,608\fR.
.RE
+.sp
+.ne 2
+.na
+\fBmetaslab_aliquot\fR (ulong)
+.ad
+.RS 12n
+Metaslab granularity, in bytes. This is roughly similar to what would be
+referred to as the "stripe size" in traditional RAID arrays. In normal
+operation, ZFS will try to write this amount of data to a top-level vdev
+before moving on to the next one.
+.sp
+Default value: \fB524,288\fR.
+.RE
+
.sp
.ne 2
.na
Default value: 10000
.RE
+.sp
+.ne 2
+.na
+\fBspa_slop_shift\fR (int)
+.ad
+.RS 12n
+Normally, we don't allow the last 3.2% (1/(2^spa_slop_shift)) of space
+in the pool to be consumed. This ensures that we don't run the pool
+completely out of space, due to unaccounted changes (e.g. to the MOS).
+It also limits the worst-case time to allocate space. If we have
+less than this amount of free space, most ZPL operations (e.g. write,
+create) will return ENOSPC.
+.sp
+Default value: 5
+.RE
+
.sp
.ne 2
.na
Default value: \fB8192\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_arc_evict_batch_limit\fR (int)
+.ad
+.RS 12n
+Number ARC headers to evict per sub-list before proceeding to another sub-list.
+This batch-style operation prevents entire sub-lists from being evicted at once
+but comes at a cost of additional unlocking and locking.
+.sp
+Default value: \fB10\fR.
+.RE
+
.sp
.ne 2
.na
.sp
.ne 2
.na
-\fBzfs_arc_max\fR (ulong)
+\fBzfs_arc_lotsfree_percent\fR (int)
.ad
.RS 12n
-Max arc size
+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: \fB0\fR.
+Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
-\fBzfs_arc_memory_throttle_disable\fR (int)
+\fBzfs_arc_max\fR (ulong)
.ad
.RS 12n
-Disable memory throttle
+Max arc size
.sp
-Use \fB1\fR for yes (default) and \fB0\fR to disable.
+Default value: \fB0\fR.
.RE
.sp
Default value: \fB0\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_arc_meta_min\fR (ulong)
+.ad
+.RS 12n
+The minimum allowed size in bytes that meta data buffers may consume in
+the ARC. This value defaults to 0 which disables a floor on the amount
+of the ARC devoted meta data.
+.sp
+Default value: \fB0\fR.
+.RE
+
.sp
.ne 2
.na
Default value: \fB100\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_arc_num_sublists_per_state\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.
+.sp
+Default value: 1 or the number of on-online CPUs, whichever is greater
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_overflow_shift\fR (int)
+.ad
+.RS 12n
+The ARC size is considered to be overflowing if it exceeds the current
+ARC target size (arc_c) by a threshold determined by this parameter.
+The threshold is calculated as a fraction of arc_c using the formula
+"arc_c >> \fBzfs_arc_overflow_shift\fR".
+
+The default value of 8 causes the ARC to be considered to be overflowing
+if it exceeds the target size by 1/256th (0.3%) of the target size.
+
+When the ARC is overflowing, new buffer allocations are stalled until
+the reclaim thread catches up and the overflow condition no longer exists.
+.sp
+Default value: \fB8\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
Default value: \fB5\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_arc_sys_free\fR (ulong)
+.ad
+.RS 12n
+The target number of bytes the ARC should leave as free memory on the system.
+Defaults to the larger of 1/64 of physical memory or 512K. Setting this
+option to a non-zero value will override the default.
+.sp
+Default value: \fB0\fR.
+.RE
+
.sp
.ne 2
.na
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_dbgmsg_enable\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.
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_dbgmsg_maxsize\fR (int)
+.ad
+.RS 12n
+The maximum size in bytes of the internal ZFS debug log.
+.sp
+Default value: \fB4M\fR.
+.RE
+
.sp
.ne 2
.na
Default value: \fB300\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzfs_admin_snapshot\fR (int)
+.ad
+.RS 12n
+Allow the creation, removal, or renaming of entries in the .zfs/snapshot
+directory to cause the creation, destruction, or renaming of snapshots.
+When enabled this functionality works both locally and over NFS exports
+which have the 'no_root_squash' option set. This functionality is disabled
+by default.
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
.sp
.ne 2
.na
Default value: \fB32,768\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 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.
+.sp
+Default value: \fB1,048,576\fR.
+.RE
+
.sp
.ne 2
.na
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
-the threshold, the allocator will avoid allocating to that group
+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
\fBzio_delay_max\fR (int)
.ad
.RS 12n
-Max zio millisec delay before posting event
+Max zio millisecond delay before posting event
.sp
Default value: \fB30,000\fR.
.RE
Default value: \fB0\fR.
.RE
+.sp
+.ne 2
+.na
+\fBzio_taskq_batch_pct\fR (uint)
+.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
+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
+latency issues and inconsistent application performance, especially when high
+compression is enabled.
+.sp
+Default value: \fB75\fR.
+.RE
+
.sp
.ne 2
.na
.sp
.ne 2
.na
-\fBzvol_threads\fR (uint)
+\fBzvol_prefetch_bytes\fR (uint)
.ad
.RS 12n
-Number of threads for zvol device
+When adding a zvol to the system prefetch \fBzvol_prefetch_bytes\fR
+from the start and end of the volume. Prefetching these regions
+of the volume is desirable because they are likely to be accessed
+immediately by \fBblkid(8)\fR or by the kernel scanning for a partition
+table.
.sp
-Default value: \fB32\fR.
+Default value: \fB131,072\fR.
.RE
.SH ZFS I/O SCHEDULER
projects / mirror_zfs.git / blobdiff