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cddl/contrib/opensolaris/cmd/zpool/zpool-features.7

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.\" Copyright (c) 2012, Martin Matuska <mm@FreeBSD.org>. .\" Copyright (c) 2012, Martin Matuska <mm@FreeBSD.org>. All Rights Reserved.
.\" All Rights Reserved. .\" Copyright (c) 2013, 2017 by Delphix. All rights reserved.
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.\" Copyright (c) 2012, 2017 by Delphix. All rights reserved.
.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved. .\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
.\" Copyright (c) 2013, Joyent, Inc. All rights reserved. .\" Copyright (c) 2014, Joyent, Inc. All rights reserved.
.\" Copyright (c) 2014 Integros [integros.com]
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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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.\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
.\" own identifying information:
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.\" $FreeBSD$ .\" $FreeBSD$
.\" .\"
.Dd June 7, 2017 .TH ZPOOL-FEATURES 7 "Dec 9, 2018"
.Dt ZPOOL-FEATURES 7 .SH NAME
.Os zpool\-features \- ZFS pool feature descriptions
.Sh NAME .SH DESCRIPTION
.Nm zpool-features .LP
.Nd ZFS pool feature descriptions
.Sh DESCRIPTION
ZFS pool on\-disk format versions are specified via "features" which replace ZFS pool on\-disk format versions are specified via "features" which replace
the old on\-disk format numbers (the last supported on\-disk format number is the old on\-disk format numbers (the last supported on\-disk format number is
28). 28). To enable a feature on a pool use the \fBupgrade\fR subcommand of the
To enable a feature on a pool use the \fBzpool\fR(8) command, or set the \fBfeature@\fR\fIfeature_name\fR property
.Cm upgrade to \fBenabled\fR.
subcommand of the .sp
.Xr zpool 8 .LP
command, or set the
.Sy feature@feature_name
property to
.Ar enabled .
.Pp
The pool format does not affect file system version compatibility or the ability The pool format does not affect file system version compatibility or the ability
to send file systems between pools. to send file systems between pools.
.Pp .sp
.LP
Since most features can be enabled independently of each other the on\-disk Since most features can be enabled independently of each other the on\-disk
format of the pool is specified by the set of all features marked as format of the pool is specified by the set of all features marked as
.Sy active \fBactive\fR on the pool. If the pool was created by another software version
on the pool. this set may include unsupported features.
If the pool was created by another software version this set may .SS "Identifying features"
include unsupported features. .LP
.Ss Identifying features Every feature has a guid of the form \fIcom.example:feature_name\fR. The reverse
Every feature has a guid of the form DNS name ensures that the feature's guid is unique across all ZFS
.Sy com.example:feature_name . implementations. When unsupported features are encountered on a pool they will
The reverse DNS name ensures that the feature's guid is unique across all ZFS be identified by their guids. Refer to the documentation for the ZFS
implementations. implementation that created the pool for information about those features.
When unsupported features are encountered on a pool they will .sp
be identified by their guids. .LP
Refer to the documentation for the ZFS implementation that created the pool Each supported feature also has a short name. By convention a feature's short
for information about those features. name is the portion of its guid which follows the ':' (e.g.
.Pp \fIcom.example:feature_name\fR would have the short name \fIfeature_name\fR),
Each supported feature also has a short name.
By convention a feature's short name is the portion of its guid which follows
the ':' (e.g.
.Sy com.example:feature_name
would have the short name
.Sy feature_name ),
however a feature's short name may differ across ZFS implementations if however a feature's short name may differ across ZFS implementations if
following the convention would result in name conflicts. following the convention would result in name conflicts.
.Ss Feature states .SS "Feature states"
.LP
Features can be in one of three states: Features can be in one of three states:
.Bl -tag -width "XXXXXXXX" .sp
.It Sy active .ne 2
This feature's on\-disk format changes are in effect on the pool. .na
Support for this feature is required to import the pool in read\-write mode. \fB\fBactive\fR\fR
If this feature is not read-only compatible, support is also required to .ad
import the pool in read\-only mode (see "Read\-only compatibility"). .RS 12n
.It Sy enabled This feature's on\-disk format changes are in effect on the pool. Support for
this feature is required to import the pool in read\-write mode. If this
feature is not read-only compatible, support is also required to import the pool
in read\-only mode (see "Read\-only compatibility").
.RE
.sp
.ne 2
.na
\fB\fBenabled\fR\fR
.ad
.RS 12n
An administrator has marked this feature as enabled on the pool, but the An administrator has marked this feature as enabled on the pool, but the
feature's on\-disk format changes have not been made yet. feature's on\-disk format changes have not been made yet. The pool can still be
The pool can still be imported by software that does not support this feature, imported by software that does not support this feature, but changes may be made
but changes may be made to the on\-disk format at any time which will move to the on\-disk format at any time which will move the feature to the
the feature to the \fBactive\fR state. Some features may support returning to the \fBenabled\fR
.Sy active state after becoming \fBactive\fR. See feature\-specific documentation for
state. details.
Some features may support returning to the .RE
.Sy enabled
state after becoming .sp
.Sy active . .ne 2
See feature\-specific documentation for details. .na
.It Sy disabled \fBdisabled\fR
.ad
.RS 12n
This feature's on\-disk format changes have not been made and will not be made This feature's on\-disk format changes have not been made and will not be made
unless an administrator moves the feature to the unless an administrator moves the feature to the \fBenabled\fR state. Features
.Sy enabled cannot be disabled once they have been enabled.
state. .RE
Features cannot be disabled once they have been enabled.
.El .sp
.Pp .LP
The state of supported features is exposed through pool properties of the form The state of supported features is exposed through pool properties of the form
.Sy feature@short_name . \fIfeature@short_name\fR.
.Ss Read\-only compatibility .SS "Read\-only compatibility"
.LP
Some features may make on\-disk format changes that do not interfere with other Some features may make on\-disk format changes that do not interfere with other
software's ability to read from the pool. software's ability to read from the pool. These features are referred to as
These features are referred to as "read\-only compatible". "read\-only compatible". If all unsupported features on a pool are read\-only
If all unsupported features on a pool are read\-only compatible, the pool can compatible, the pool can be imported in read\-only mode by setting the
be imported in read\-only mode by setting the \fBreadonly\fR property during import (see \fBzpool\fR(8) for details on
.Sy readonly importing pools).
property during import (see .SS "Unsupported features"
.Xr zpool 8 .LP
for details on importing pools).
.Ss Unsupported features
For each unsupported feature enabled on an imported pool a pool property For each unsupported feature enabled on an imported pool a pool property
named named \fIunsupported@feature_guid\fR will indicate why the import was allowed
.Sy unsupported@feature_guid despite the unsupported feature. Possible values for this property are:
will indicate why the import was allowed despite the unsupported feature.
Possible values for this property are: .sp
.Bl -tag -width "XXXXXXXX" .ne 2
.It Sy inactive .na
The feature is in the \fB\fBinactive\fR\fR
.Sy enabled .ad
state and therefore the pool's on\-disk format is still compatible with .RS 12n
software that does not support this feature. The feature is in the \fBenabled\fR state and therefore the pool's on\-disk
.It Sy readonly format is still compatible with software that does not support this feature.
.RE
.sp
.ne 2
.na
\fB\fBreadonly\fR\fR
.ad
.RS 12n
The feature is read\-only compatible and the pool has been imported in The feature is read\-only compatible and the pool has been imported in
read\-only mode. read\-only mode.
.El .RE
.Ss Feature dependencies
.SS "Feature dependencies"
.LP
Some features depend on other features being enabled in order to function Some features depend on other features being enabled in order to function
properly. properly. Enabling a feature will automatically enable any features it
Enabling a feature will automatically enable any features it depends on. depends on.
.Sh FEATURES .SH FEATURES
.LP
The following features are supported on this system: The following features are supported on this system:
.Bl -tag -width "XXXXXXXX" .sp
.It Sy async_destroy .ne 2
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:async_destroy" .na
.It GUID Ta com.delphix:async_destroy \fB\fBasync_destroy\fR\fR
.It READ\-ONLY COMPATIBLE Ta yes .ad
.It DEPENDENCIES Ta none .RS 4n
.El .TS
.Pp l l .
GUID com.delphix:async_destroy
READ\-ONLY COMPATIBLE yes
DEPENDENCIES none
.TE
Destroying a file system requires traversing all of its data in order to Destroying a file system requires traversing all of its data in order to
return its used space to the pool. return its used space to the pool. Without \fBasync_destroy\fR the file system
Without is not fully removed until all space has been reclaimed. If the destroy
.Sy async_destroy operation is interrupted by a reboot or power outage the next attempt to open
the file system is not fully removed until all space has been reclaimed. the pool will need to complete the destroy operation synchronously.
If the destroy operation is interrupted by a reboot or power outage the next
attempt to open the pool will need to complete the destroy operation When \fBasync_destroy\fR is enabled the file system's data will be reclaimed
synchronously. by a background process, allowing the destroy operation to complete without
.Pp traversing the entire file system. The background process is able to resume
When interrupted destroys after the pool has been opened, eliminating the need
.Sy async_destroy to finish interrupted destroys as part of the open operation. The amount
is enabled the file system's data will be reclaimed by a background process, of space remaining to be reclaimed by the background process is available
allowing the destroy operation to complete without traversing the entire file through the \fBfreeing\fR property.
system.
The background process is able to resume interrupted destroys after the pool This feature is only \fBactive\fR while \fBfreeing\fR is non\-zero.
has been opened, eliminating the need to finish interrupted destroys as part .RE
of the open operation.
The amount of space remaining to be reclaimed by the background process is .sp
available through the .ne 2
.Sy freeing .na
property. \fB\fBempty_bpobj\fR\fR
.Pp .ad
This feature is only .RS 4n
.Sy active .TS
while l l .
.Sy freeing GUID com.delphix:empty_bpobj
is non\-zero. READ\-ONLY COMPATIBLE yes
.It Sy empty_bpobj DEPENDENCIES none
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:empty_bpobj" .TE
.It GUID Ta com.delphix:empty_bpobj
.It READ\-ONLY COMPATIBLE Ta yes This feature increases the performance of creating and using a large
.It DEPENDENCIES Ta none number of snapshots of a single filesystem or volume, and also reduces
.El the disk space required.
.Pp
This feature increases the performance of creating and using a large number When there are many snapshots, each snapshot uses many Block Pointer
of snapshots of a single filesystem or volume, and also reduces the disk Objects (bpobj's) to track blocks associated with that snapshot.
space required. However, in common use cases, most of these bpobj's are empty. This
.Pp feature allows us to create each bpobj on-demand, thus eliminating the
When there are many snapshots, each snapshot uses many Block Pointer Objects
.Pq bpobj's
to track blocks associated with that snapshot.
However, in common use cases, most of these bpobj's are empty.
This feature allows us to create each bpobj on-demand, thus eliminating the
empty bpobjs. empty bpobjs.
.Pp
This feature is This feature is \fBactive\fR while there are any filesystems, volumes,
.Sy active or snapshots which were created after enabling this feature.
while there are any filesystems, volumes, or snapshots which were created .RE
after enabling this feature.
.It Sy filesystem_limits .sp
.Bl -column "READ\-ONLY COMPATIBLE" "com.joyent:filesystem_limits" .ne 2
.It GUID Ta com.joyent:filesystem_limits .na
.It READ\-ONLY COMPATIBLE Ta yes \fB\fBfilesystem_limits\fR\fR
.It DEPENDENCIES Ta extensible_dataset .ad
.El .RS 4n
.Pp .TS
This feature enables filesystem and snapshot limits. l l .
These limits can be used GUID com.joyent:filesystem_limits
READ\-ONLY COMPATIBLE yes
DEPENDENCIES extensible_dataset
.TE
This feature enables filesystem and snapshot limits. These limits can be used
to control how many filesystems and/or snapshots can be created at the point in to control how many filesystems and/or snapshots can be created at the point in
the tree on which the limits are set. the tree on which the limits are set.
.Pp
This feature is This feature is \fBactive\fR once either of the limit properties has been
.Sy active set on a dataset. Once activated the feature is never deactivated.
once either of the limit properties has been .RE
set on a dataset.
Once activated the feature is never deactivated. .sp
.It Sy lz4_compress .ne 2
.Bl -column "READ\-ONLY COMPATIBLE" "org.illumos:lz4_compress" .na
.It GUID Ta org.illumos:lz4_compress \fB\fBlz4_compress\fR\fR
.It READ\-ONLY COMPATIBLE Ta no .ad
.It DEPENDENCIES Ta none .RS 4n
.El .TS
.Pp l l .
.Sy lz4 GUID org.illumos:lz4_compress
is a high-performance real-time compression algorithm that READ\-ONLY COMPATIBLE no
DEPENDENCIES none
.TE
\fBlz4\fR is a high-performance real-time compression algorithm that
features significantly faster compression and decompression as well as a features significantly faster compression and decompression as well as a
higher compression ratio than the older higher compression ratio than the older \fBlzjb\fR compression.
.Sy lzjb Typically, \fBlz4\fR compression is approximately 50% faster on
compression.
Typically,
.Sy lz4
compression is approximately 50% faster on
compressible data and 200% faster on incompressible data than compressible data and 200% faster on incompressible data than
.Sy lzjb . \fBlzjb\fR. It is also approximately 80% faster on decompression, while
It is also approximately 80% faster on decompression, while
giving approximately 10% better compression ratio. giving approximately 10% better compression ratio.
.Pp
When the When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the
.Sy lz4_compress administrator can turn on \fBlz4\fR compression on any dataset on the
feature is set to pool using the \fBzfs\fR(8) command. Also, all newly written metadata
.Sy enabled , will be compressed with \fBlz4\fR algorithm. Since this feature is not
the read-only compatible, this operation will render the pool unimportable
administrator can turn on on systems without support for the \fBlz4_compress\fR feature. Booting
.Sy lz4 off of \fBlz4\fR-compressed root pools is supported.
compression on any dataset on the
pool using the This feature becomes \fBactive\fR as soon as it is enabled and will
.Xr zfs 8 never return to being \fBenabled\fR.
command. .RE
Also, all newly written metadata
will be compressed with .sp
.Sy lz4 .ne 2
algorithm. .na
Since this feature is not read-only compatible, this \fB\fBspacemap_histogram\fR\fR
operation will render the pool unimportable on systems without support .ad
for the .RS 4n
.Sy lz4_compress .TS
feature. l l .
Booting off of GUID com.delphix:spacemap_histogram
.Sy lz4 READ\-ONLY COMPATIBLE yes
-compressed root pools is supported. DEPENDENCIES none
.Pp .TE
This feature becomes
.Sy active This features allows ZFS to maintain more information about how free space
as soon as it is enabled and will is organized within the pool. If this feature is \fBenabled\fR, ZFS will
never return to being set this feature to \fBactive\fR when a new space map object is created or
.Sy enabled . an existing space map is upgraded to the new format. Once the feature is
.It Sy multi_vdev_crash_dump \fBactive\fR, it will remain in that state until the pool is destroyed.
.Bl -column "READ\-ONLY COMPATIBLE" "com.joyent:multi_vdev_crash_dump" .RE
.It GUID Ta com.joyent:multi_vdev_crash_dump
.It READ\-ONLY COMPATIBLE Ta no .sp
.It DEPENDENCIES Ta none .ne 2
.El .na
.Pp \fB\fBmulti_vdev_crash_dump\fR\fR
.ad
.RS 4n
.TS
l l .
GUID com.joyent:multi_vdev_crash_dump
READ\-ONLY COMPATIBLE no
DEPENDENCIES none
.TE
This feature allows a dump device to be configured with a pool comprised This feature allows a dump device to be configured with a pool comprised
of multiple vdevs. of multiple vdevs. Those vdevs may be arranged in any mirrored or raidz
Those vdevs may be arranged in any mirrored or raidz
configuration. configuration.
.\" TODO: this is not yet supported on FreeBSD.
.\" .Pp Under FreeBSD this feature is registered for compatibility but not used.
.\" When the New pools created under FreeBSD will have the feature \fBenabled\fR but
.\" .Sy multi_vdev_crash_dump will never transition to \fB\fBactive\fR. Existing pools
.\" feature is set to where this feature is \fB\fBactive\fR can be imported.
.\" .Sy enabled , .RE
.\" the administrator can use the
.\" .Xr dumpon 8 .sp
.\" command to configure a .ne 2
.\" dump device on a pool comprised of multiple vdevs. .na
.It Sy spacemap_histogram \fB\fBextensible_dataset\fR\fR
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:spacemap_histogram" .ad
.It GUID Ta com.delphix:spacemap_histogram .RS 4n
.It READ\-ONLY COMPATIBLE Ta yes .TS
.It DEPENDENCIES Ta none l l .
.El GUID com.delphix:extensible_dataset
.Pp READ\-ONLY COMPATIBLE no
This features allows ZFS to maintain more information about how free space DEPENDENCIES none
is organized within the pool. .TE
If this feature is
.Sy enabled ,
ZFS will
set this feature to
.Sy active
when a new space map object is created or
an existing space map is upgraded to the new format.
Once the feature is
.Sy active ,
it will remain in that state until the pool is destroyed.
.It Sy extensible_dataset
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:extensible_dataset"
.It GUID Ta com.delphix:extensible_dataset
.It READ\-ONLY COMPATIBLE Ta no
.It DEPENDENCIES Ta none
.El
.Pp
This feature allows more flexible use of internal ZFS data structures, This feature allows more flexible use of internal ZFS data structures,
and exists for other features to depend on. and exists for other features to depend on.
.Pp
This feature will be This feature will be \fBactive\fR when the first dependent feature uses it,
.Sy active and will be returned to the \fBenabled\fR state when all datasets that use
when the first dependent feature uses it,
and will be returned to the
.Sy enabled
state when all datasets that use
this feature are destroyed. this feature are destroyed.
.It Sy bookmarks
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:bookmarks" .RE
.It GUID Ta com.delphix:bookmarks
.It READ\-ONLY COMPATIBLE Ta yes .sp
.It DEPENDENCIES Ta extensible_dataset .ne 2
.El .na
.Pp \fB\fBbookmarks\fR\fR
This feature enables use of the .ad
.Nm zfs .RS 4n
.Cm bookmark .TS
subcommand. l l .
.Pp GUID com.delphix:bookmarks
This feature is READ\-ONLY COMPATIBLE yes
.Sy active DEPENDENCIES extensible_dataset
while any bookmarks exist in the pool. .TE
This feature enables use of the \fBzfs bookmark\fR subcommand.
This feature is \fBactive\fR while any bookmarks exist in the pool.
All bookmarks in the pool can be listed by running All bookmarks in the pool can be listed by running
.Nm zfs \fBzfs list -t bookmark -r \fIpoolname\fR\fR.
.Cm list
.Fl t No bookmark Fl r Ar poolname . .RE
.It Sy enabled_txg
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:enabled_txg" .sp
.It GUID Ta com.delphix:enabled_txg .ne 2
.It READ\-ONLY COMPATIBLE Ta yes .na
.It DEPENDENCIES Ta none \fB\fBenabled_txg\fR\fR
.El .ad
.Pp .RS 4n
.TS
l l .
GUID com.delphix:enabled_txg
READ\-ONLY COMPATIBLE yes
DEPENDENCIES none
.TE
Once this feature is enabled ZFS records the transaction group number Once this feature is enabled ZFS records the transaction group number
in which new features are enabled. in which new features are enabled. This has no user-visible impact,
This has no user-visible impact,
but other features may depend on this feature. but other features may depend on this feature.
.Pp
This feature becomes This feature becomes \fBactive\fR as soon as it is enabled and will
.Sy active never return to being \fBenabled\fR.
as soon as it is enabled and will
never return to being .RE
.Sy enabled .
.It Sy hole_birth .sp
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:hole_birth" .ne 2
.It GUID Ta com.delphix:hole_birth .na
.It READ\-ONLY COMPATIBLE Ta no \fB\fBhole_birth\fR\fR
.It DEPENDENCIES Ta enabled_txg .ad
.El .RS 4n
.Pp .TS
This feature improves performance of incremental sends l l .
.Pq Dq zfs send -i GUID com.delphix:hole_birth
and receives for objects with many holes. READ\-ONLY COMPATIBLE no
The most common case of DEPENDENCIES enabled_txg
.TE
This feature improves performance of incremental sends ("zfs send -i")
and receives for objects with many holes. The most common case of
hole-filled objects is zvols. hole-filled objects is zvols.
.Pp
An incremental send stream from snapshot An incremental send stream from snapshot \fBA\fR to snapshot \fBB\fR
.Sy A contains information about every block that changed between \fBA\fR and
to snapshot \fBB\fR. Blocks which did not change between those snapshots can be
.Sy B
contains information about every block that changed between
.Sy A
and
.Sy B .
Blocks which did not change between those snapshots can be
identified and omitted from the stream using a piece of metadata called identified and omitted from the stream using a piece of metadata called
the 'block birth time', but birth times are not recorded for holes the 'block birth time', but birth times are not recorded for holes (blocks
.Pq blocks filled only with zeroes . filled only with zeroes). Since holes created after \fBA\fR cannot be
Since holes created after distinguished from holes created before \fBA\fR, information about every
.Sy A
cannot be
distinguished from holes created before
.Sy A ,
information about every
hole in the entire filesystem or zvol is included in the send stream. hole in the entire filesystem or zvol is included in the send stream.
.Pp
For workloads where holes are rare this is not a problem. For workloads where holes are rare this is not a problem. However, when
However, when incrementally replicating filesystems or zvols with many holes (for
incrementally replicating filesystems or zvols with many holes example a zvol formatted with another filesystem) a lot of time will
.Pq for example a zvol formatted with another filesystem
a lot of time will
be spent sending and receiving unnecessary information about holes that be spent sending and receiving unnecessary information about holes that
already exist on the receiving side. already exist on the receiving side.
.Pp
Once the Once the \fBhole_birth\fR feature has been enabled the block birth times
.Sy hole_birth of all new holes will be recorded. Incremental sends between snapshots
feature has been enabled the block birth times
of all new holes will be recorded.
Incremental sends between snapshots
created after this feature is enabled will use this new metadata to avoid created after this feature is enabled will use this new metadata to avoid
sending information about holes that already exist on the receiving side. sending information about holes that already exist on the receiving side.
.Pp
This feature becomes This feature becomes \fBactive\fR as soon as it is enabled and will
.Sy active never return to being \fBenabled\fR.
as soon as it is enabled and will
never return to being .RE
.Sy enabled .
.It Sy embedded_data .sp
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:embedded_data" .ne 2
.It GUID Ta com.delphix:embedded_data .na
.It READ\-ONLY COMPATIBLE Ta no \fB\fBembedded_data\fR\fR
.It DEPENDENCIES Ta none .ad
.El .RS 4n
.Pp .TS
l l .
GUID com.delphix:embedded_data
READ\-ONLY COMPATIBLE no
DEPENDENCIES none
.TE
This feature improves the performance and compression ratio of This feature improves the performance and compression ratio of
highly-compressible blocks. highly-compressible blocks. Blocks whose contents can compress to 112 bytes
Blocks whose contents can compress to 112 bytes
or smaller can take advantage of this feature. or smaller can take advantage of this feature.
.Pp
When this feature is enabled, the contents of highly-compressible blocks are When this feature is enabled, the contents of highly-compressible blocks are
stored in the block "pointer" itself stored in the block "pointer" itself (a misnomer in this case, as it contains
.Po a misnomer in this case, as it contains the compresseed data, rather than a pointer to its location on disk). Thus
the compressed data, rather than a pointer to its location on disk the space of the block (one sector, typically 512 bytes or 4KB) is saved,
.Pc .
Thus
the space of the block
.Pq one sector, typically 512 bytes or 4KB
is saved,
and no additional i/o is needed to read and write the data block. and no additional i/o is needed to read and write the data block.
.Pp
This feature becomes This feature becomes \fBactive\fR as soon as it is enabled and will
.Sy active never return to being \fBenabled\fR.
as soon as it is enabled and will
never return to being .RE
.Sy enabled . .sp
.It Sy zpool_checkpoint .ne 2
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:zpool_checkpoint" .na
.It GUID Ta com.delphix:zpool_checkpoint \fB\fBdevice_removal\fR\fR
.It READ\-ONLY COMPATIBLE Ta yes .ad
.It DEPENDENCIES Ta none .RS 4n
.El .TS
.Pp l l .
This feature enables the "zpool checkpoint" subcommand that can GUID com.delphix:device_removal
checkpoint the state of the pool at the time it was issued and later READ\-ONLY COMPATIBLE no
rewind back to it or discard it. DEPENDENCIES none
.Pp .TE
This feature becomes
.Sy active
when the "zpool checkpoint" command is used to checkpoint the pool.
The feature will only return back to being
.Sy enabled
when the pool is rewound or the checkpoint has been discarded.
.It Sy device_removal
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:device_removal"
.It GUID Ta com.delphix:device_removal
.It READ\-ONLY COMPATIBLE Ta no
.It DEPENDENCIES Ta none
.El
.Pp
This feature enables the "zpool remove" subcommand to remove top-level This feature enables the "zpool remove" subcommand to remove top-level
vdevs, evacuating them to reduce the total size of the pool. vdevs, evacuating them to reduce the total size of the pool.
.Pp
This feature becomes This feature becomes \fBactive\fR when the "zpool remove" command is used
.Sy active on a top-level vdev, and will never return to being \fBenabled\fR.
when the "zpool remove" command is used
on a top-level vdev, and will never return to being .RE
.Sy enabled . .sp
.It Sy obsolete_counts .ne 2
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:obsolete_counts" .na
.It GUID Ta com.delphix:obsolete_counts \fB\fBobsolete_counts\fR\fR
.It READ\-ONLY COMPATIBLE Ta yes .ad
.It DEPENDENCIES Ta device_removal .RS 4n
.El .TS
.Pp l l .
GUID com.delphix:obsolete_counts
READ\-ONLY COMPATIBLE yes
DEPENDENCIES device_removal
.TE
This feature is an enhancement of device_removal, which will over time This feature is an enhancement of device_removal, which will over time
reduce the memory used to track removed devices. When indirect blocks reduce the memory used to track removed devices. When indirect blocks
are freed or remapped, we note that their part of the indirect mapping are freed or remapped, we note that their part of the indirect mapping
is "obsolete", i.e. no longer needed. See also the "zfs remap" is "obsolete", i.e. no longer needed. See also the \fBzfs remap\fR
subcommand in subcommand in \fBzfs\fR(8).
.Xr zfs 8 .
This feature becomes This feature becomes \fBactive\fR when the "zpool remove" command is
.Sy active used on a top-level vdev, and will never return to being \fBenabled\fR.
when the "zpool remove" command is
used on a top-level vdev, and will never return to being .RE
.Sy enabled . .sp
.It Sy spacemap_v2 .ne 2
.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:spacemap_v2" .na
.It GUID Ta com.delphix:spacemap_v2 \fB\fBzpool_checkpoint\fR\fR
.It READ\-ONLY COMPATIBLE Ta yes .ad
.It DEPENDENCIES Ta none .RS 4n
.El .TS
.Pp l l .
GUID com.delphix:zpool_checkpoint
READ\-ONLY COMPATIBLE yes
DEPENDENCIES none
.TE
This feature enables the "zpool checkpoint" subcommand that can
checkpoint the state of the pool at the time it was issued and later
rewind back to it or discard it.
This feature becomes \fBactive\fR when the "zpool checkpoint" command
is used to checkpoint the pool.
The feature will only return back to being \fBenabled\fR when the pool
is rewound or the checkpoint has been discarded.
.RE
.sp
.ne 2
.na
\fB\fBspacemap_v2\fR\fR
.ad
.RS 4n
.TS
l l .
GUID com.delphix:spacemap_v2
READ\-ONLY COMPATIBLE yes
DEPENDENCIES none
.TE
This feature enables the use of the new space map encoding which This feature enables the use of the new space map encoding which
consists of two words (instead of one) whenever it is advantageous. consists of two words (instead of one) whenever it is advantageous.
The new encoding allows space maps to represent large regions of The new encoding allows space maps to represent large regions of
space more efficiently on-disk while also increasing their maximum space more efficiently on-disk while also increasing their maximum
addressable offset. addressable offset.
.Pp
This feature becomes This feature becomes \fBactive\fR once it is \fBenabled\fR, and never
.Sy active returns back to being \fBenabled\fR.
as soon as it is enabled and will
never return to being .RE
.Sy enabled . .sp
.It Sy large_blocks .ne 2
.Bl -column "READ\-ONLY COMPATIBLE" "org.open-zfs:large_block" .na
.It GUID Ta org.open-zfs:large_block \fB\fBlarge_blocks\fR\fR
.It READ\-ONLY COMPATIBLE Ta no .ad
.It DEPENDENCIES Ta extensible_dataset .RS 4n
.El .TS
.Pp l l .
The GUID org.open-zfs:large_block
.Sy large_block READ\-ONLY COMPATIBLE no
feature allows the record size on a dataset to be DEPENDENCIES extensible_dataset
.TE
The \fBlarge_block\fR feature allows the record size on a dataset to be
set larger than 128KB. set larger than 128KB.
.Pp
This feature becomes This feature becomes \fBactive\fR once a \fBrecordsize\fR property has been
.Sy active set larger than 128KB, and will return to being \fBenabled\fR once all
once a filesystems that have ever had their recordsize larger than 128KB are destroyed.
.Sy recordsize .RE
property has been set larger than 128KB, and will return to being
.Sy enabled .sp
once all filesystems that have ever had their recordsize larger than 128KB .ne 2
are destroyed. .na
.Pp \fB\fBsha512\fR\fR
Please note that booting from datasets that have recordsize greater than .ad
128KB is .RS 4n
.Em NOT .TS
supported by the l l .
.Fx GUID org.illumos:sha512
boot loader. READ\-ONLY COMPATIBLE no
.It Sy sha512 DEPENDENCIES extensible_dataset
.Bl -column "READ\-ONLY COMPATIBLE" "org.illumos:sha512" .TE
.It GUID Ta org.illumos:sha512
.It READ\-ONLY COMPATIBLE Ta no This feature enables the use of the SHA-512/256 truncated hash algorithm
.It DEPENDENCIES Ta none (FIPS 180-4) for checksum and dedup. The native 64-bit arithmetic of
.El SHA-512 provides an approximate 50% performance boost over SHA-256 on
.Pp 64-bit hardware and is thus a good minimum-change replacement candidate
The for systems where hash performance is important, but these systems
.Sy sha512 cannot for whatever reason utilize the faster \fBskein\fR and
feature enables the use of the SHA-512/256 truncated hash algorithm \fBedonr\fR algorithms.
.Pq FIPS 180-4
for checksum and dedup. When the \fBsha512\fR feature is set to \fBenabled\fR, the administrator
The native 64-bit arithmetic of SHA-512 provides an approximate 50% can turn on the \fBsha512\fR checksum on any dataset using the
performance boost over SHA-256 on 64-bit hardware and is thus a good \fBzfs set checksum=sha512\fR command. This feature becomes
minimum-change replacement candidate for systems where hash performance is \fBactive\fR once a \fBchecksum\fR property has been set to \fBsha512\fR,
important, but these systems cannot for whatever reason utilize the faster and will return to being \fBenabled\fR once all filesystems that have
.Sy skein ever had their checksum set to \fBsha512\fR are destroyed.
algorithms.
.Pp Booting off of pools utilizing SHA-512/256 is supported.
When the
.Sy sha512 .RE
feature is set to
.Sy enabled , .sp
the administrator can turn on the .ne 2
.Sy sha512 .na
checksum on any dataset using the \fB\fBskein\fR\fR
.Dl # zfs set checksum=sha512 Ar dataset .ad
command. .RS 4n
This feature becomes .TS
.Sy active l l .
once a GUID org.illumos:skein
.Sy checksum READ\-ONLY COMPATIBLE no
property has been set to DEPENDENCIES extensible_dataset
.Sy sha512 , .TE
and will return to being
.Sy enabled This feature enables the use of the Skein hash algorithm for checksum
once all filesystems that have ever had their checksum set to and dedup. Skein is a high-performance secure hash algorithm that was a
.Sy sha512 finalist in the NIST SHA-3 competition. It provides a very high security
are destroyed. margin and high performance on 64-bit hardware (80% faster than
.It Sy skein SHA-256). This implementation also utilizes the new salted checksumming
.Bl -column "READ\-ONLY COMPATIBLE" "org.illumos:skein" functionality in ZFS, which means that the checksum is pre-seeded with a
.It GUID Ta org.illumos:skein secret 256-bit random key (stored on the pool) before being fed the data
.It READ\-ONLY COMPATIBLE Ta no block to be checksummed. Thus the produced checksums are unique to a
.It DEPENDENCIES Ta none given pool, preventing hash collision attacks on systems with dedup.
.El
.Pp When the \fBskein\fR feature is set to \fBenabled\fR, the administrator
The can turn on the \fBskein\fR checksum on any dataset using the
.Sy skein \fBzfs set checksum=skein\fR command. This feature becomes
feature enables the use of the Skein hash algorithm for checksum and dedup. \fBactive\fR once a \fBchecksum\fR property has been set to \fBskein\fR,
Skein is a high-performance secure hash algorithm that was a finalist in the and will return to being \fBenabled\fR once all filesystems that have
NIST SHA-3 competition. ever had their checksum set to \fBskein\fR are destroyed.
It provides a very high security margin and high performance on 64-bit hardware
.Pq 80% faster than SHA-256 . Booting off of pools using \fBskein\fR is supported.
This implementation also utilizes the new salted checksumming functionality in
ZFS, which means that the checksum is pre-seeded with a secret 256-bit random .SH "SEE ALSO"
key \fBzfs\fR(8), \fBzpool\fR(8)
.Pq stored on the pool
before being fed the data block to be checksummed.
Thus the produced checksums are unique to a given pool, preventing hash
collision attacks on systems with dedup.
.Pp
When the
.Sy skein
feature is set to
.Sy enabled ,
the administrator can turn on the
.Sy skein
checksum on any dataset using the
.Dl # zfs set checksum=skein Ar dataset
command.
This feature becomes
.Sy active
once a
.Sy checksum
property has been set to
.Sy skein ,
and will return to being
.Sy enabled
once all filesystems that have ever had their checksum set to
.Sy skein
are destroyed.
.El
.Sh SEE ALSO
.Xr zpool 8
.Sh AUTHORS
This manual page is a
.Xr mdoc 7
reimplementation of the
.Tn illumos
manual page
.Em zpool-features(5) ,
modified and customized for
.Fx
and licensed under the Common Development and Distribution License
.Pq Tn CDDL .
.Pp
The
.Xr mdoc 7
implementation of this manual page was initially written by
.An Martin Matuska Aq mm@FreeBSD.org .