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ZPOOL-FEATURES(7)  FreeBSD Miscellaneous Information Manual  ZPOOL-FEATURES(7)

NAME
     zpool-features -- description of ZFS pool features

DESCRIPTION
     ZFS pool on-disk format versions are specified via	"features" which re-
     place the old on-disk format numbers (the last supported on-disk format
     number is 28).  To	enable a feature on a pool use the zpool upgrade, or
     set the feature@feature-name property to enabled.	Please also see	the
     Compatibility feature sets	section	for information	on how sets of fea-
     tures may be enabled together.

     The pool format does not affect file system version compatibility or the
     ability to	send file systems between pools.

     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
     active on the pool.  If the pool was created by another software version
     this set may include unsupported features.

   Identifying features
     Every feature has a GUID of the form com.example:feature-name.  The re-
     versed DNS	name ensures that the feature's	GUID is	unique across all ZFS
     implementations.  When unsupported	features are encountered on a pool
     they will be identified by	their GUIDs.  Refer to the documentation for
     the ZFS implementation that created the pool for information about	those
     features.

     Each supported feature also has a short name.  By convention a feature's
     short name	is the portion of its GUID which follows the `:' (i.e.
     com.example:feature-name would have the short name	feature-name), however
     a feature's short name may	differ across ZFS implementations if following
     the convention would result in name conflicts.

   Feature states
     Features can be in	one of three states:

     active    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 compati-
	       ble, support is also required to	import the pool	in read-only
	       mode (see Read-only compatibility).

     enabled   An administrator	has marked this	feature	as enabled on the
	       pool, but the feature's on-disk format changes have not been
	       made yet.  The pool can still be	imported by software that does
	       not support this	feature, but changes may be made to the	on-
	       disk format at any time which will move the feature to the
	       active state.  Some features may	support	returning to the
	       enabled state after becoming active.  See feature-specific doc-
	       umentation for details.

     disabled  This feature's on-disk format changes have not been made	and
	       will not	be made	unless an administrator	moves the feature to
	       the enabled state.  Features cannot be disabled once they have
	       been enabled.

     The state of supported features is	exposed	through	pool properties	of the
     form feature@short-name.

   Read-only compatibility
     Some features may make on-disk format changes that	do not interfere with
     other software's ability to read from the pool.  These features are re-
     ferred to as "read-only compatible".  If all unsupported features on a
     pool are read-only	compatible, the	pool can be imported in	read-only mode
     by	setting	the readonly property during import (see zpool-import(8) for
     details on	importing pools).

   Unsupported features
     For each unsupported feature enabled on an	imported pool, a pool property
     named unsupported@feature-name will indicate why the import was allowed
     despite the unsupported feature.  Possible	values for this	property are:

     inactive  The feature is in the enabled state and therefore the pool's
	       on-disk format is still compatible with software	that does not
	       support this feature.

     readonly  The feature is read-only	compatible and the pool	has been im-
	       ported in read-only mode.

   Feature dependencies
     Some features depend on other features being enabled in order to func-
     tion.  Enabling a feature will automatically enable any features it de-
     pends on.

   Compatibility feature sets
     It	is sometimes necessary for a pool to maintain compatibility with a
     specific on-disk format, by enabling and disabling	particular features.
     The compatibility feature facilitates this	by allowing feature sets to be
     read from text files.  When set to	off (the default), compatibility fea-
     ture sets are disabled (i.e. all features are enabled); when set to
     legacy, no	features are enabled.  When set	to a comma-separated list of
     filenames (each filename may either be an absolute	path, or relative to
     /etc/zfs/compatibility.d or /usr/share/zfs/compatibility.d), the lists of
     requested features	are read from those files, separated by	whitespace
     and/or commas.  Only features present in all files	are enabled.

     Simple sanity checks are applied to the files: they must be between 1B
     and 16kB in size, and must	end with a newline character.

     The requested features are	applied	when a pool is created using zpool
     create -o compatibility=_a|	and controls which features are	enabled	when
     using zpool upgrade.  zpool status	will not show a	warning	about disabled
     features which are	not part of the	requested feature set.

     The special value legacy prevents any features from being enabled,	either
     via zpool upgrade or zpool	set feature@feature-name=enabled.  This	set-
     ting also prevents	pools from being upgraded to newer on-disk versions.
     This is a safety measure to prevent new features from being accidentally
     enabled, breaking compatibility.

     By	convention, compatibility files	in /usr/share/zfs/compatibility.d are
     provided by the distribution, and include feature sets supported by im-
     portant versions of popular distributions,	and feature sets commonly sup-
     ported at the start of each year.	Compatibility files in
     /etc/zfs/compatibility.d, if present, will	take precedence	over files
     with the same name	in /usr/share/zfs/compatibility.d.

     If	an unrecognized	feature	is found in these files, an error message will
     be	shown.	If the unrecognized feature is in a file in
     /etc/zfs/compatibility.d, this is treated as an error and processing will
     stop.  If the unrecognized	feature	is under
     /usr/share/zfs/compatibility.d, this is treated as	a warning and process-
     ing will continue.	 This difference is to allow distributions to include
     features which might not be recognized by the currently-installed bina-
     ries.

     Compatibility files may include comments: any text	from `#' to the	end of
     the line is ignored.

     Example:
	 example# cat /usr/share/zfs/compatibility.d/grub2
	 # Features which are supported	by GRUB2
	 async_destroy
	 bookmarks
	 embedded_data
	 empty_bpobj
	 enabled_txg
	 extensible_dataset
	 filesystem_limits
	 hole_birth
	 large_blocks
	 lz4_compress
	 spacemap_histogram

	 example# zpool	create -o compatibility=grub2 bootpool vdev

     See zpool-create(8) and zpool-upgrade(8) for more information on how
     these commands are	affected by feature sets.

FEATURES
     The following features are	supported on this system:

     allocation_classes
	     GUID		   org.zfsonlinux:allocation_classes
	     READ-ONLY COMPATIBLE  yes

	     This feature enables support for separate allocation classes.

	     This feature becomes active when a	dedicated allocation class
	     vdev (dedup or special) is	created	with the zpool create or zpool
	     add commands.  With device	removal, it can	be returned to the
	     enabled state if all the dedicated	allocation class vdevs are re-
	     moved.

     async_destroy
	     GUID		   com.delphix:async_destroy
	     READ-ONLY COMPATIBLE  yes

	     Destroying	a file system requires traversing all of its data in
	     order to return its used space to the pool.  Without
	     async_destroy, the	file system is not fully removed until all
	     space has been reclaimed.	If the destroy operation is inter-
	     rupted by a reboot	or power outage, the next attempt to open the
	     pool will need to complete	the destroy operation synchronously.

	     When async_destroy	is enabled, the	file system's data will	be re-
	     claimed by	a background process, allowing the destroy operation
	     to	complete without traversing the	entire file system.  The back-
	     ground process is able to resume interrupted destroys after the
	     pool has been opened, eliminating the need	to finish interrupted
	     destroys as part of the open operation.  The amount of space re-
	     maining to	be reclaimed by	the background process is available
	     through the freeing property.

	     This feature is only active while freeing is non-zero.

     bookmarks
	     GUID		   com.delphix:bookmarks
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  yes

	     This feature enables use of the zfs bookmark command.

	     This feature is active while any bookmarks	exist in the pool.
	     All bookmarks in the pool can be listed by	running	zfs list -t
	     bookmark -r poolname.

     bookmark_v2
	     GUID		   com.datto:bookmark_v2
	     DEPENDENCIES	   bookmark, extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature enables the creation and management of larger	book-
	     marks which are needed for	other features in ZFS.

	     This feature becomes active when a	v2 bookmark is created and
	     will be returned to the enabled state when	all v2 bookmarks are
	     destroyed.

     bookmark_written
	     GUID		   com.delphix:bookmark_written
	     DEPENDENCIES	   bookmark, extensible_dataset, bookmark_v2
	     READ-ONLY COMPATIBLE  no

	     This feature enables additional bookmark accounting fields, en-
	     abling the	written#bookmark property (space written since a book-
	     mark) and estimates of send stream	sizes for incrementals from
	     bookmarks.

	     This feature becomes active when a	bookmark is created and	will
	     be	returned to the	enabled	state when all bookmarks with these
	     fields are	destroyed.

     device_rebuild
	     GUID		   org.openzfs:device_rebuild
	     READ-ONLY COMPATIBLE  yes

	     This feature enables the ability for the zpool attach and zpool
	     replace commands to perform sequential reconstruction (instead of
	     healing reconstruction) when resilvering.

	     Sequential	reconstruction resilvers a device in LBA order without
	     immediately verifying the checksums.  Once	complete, a scrub is
	     started, which then verifies the checksums.  This approach	allows
	     full redundancy to	be restored to the pool	in the minimum amount
	     of	time.  This two-phase approach will take longer	than a healing
	     resilver when the time to verify the checksums is included.  How-
	     ever, unless there	is additional pool damage, no checksum errors
	     should be reported	by the scrub.  This feature is incompatible
	     with raidz	configurations.	 This feature becomes active while a
	     sequential	resilver is in progress, and returns to	enabled	when
	     the resilver completes.

     device_removal
	     GUID		   com.delphix:device_removal
	     READ-ONLY COMPATIBLE  no

	     This feature enables the zpool remove command to remove top-level
	     vdevs, evacuating them to reduce the total	size of	the pool.

	     This feature becomes active when the zpool	remove command is used
	     on	a top-level vdev, and will never return	to being enabled.

     draid
	     GUID		   org.openzfs:draid
	     READ-ONLY COMPATIBLE  no

	     This feature enables use of the draid vdev	type.  dRAID is	a
	     variant of	raidz which provides integrated	distributed hot	spares
	     that allow	faster resilvering while retaining the benefits	of
	     raidz.  Data, parity, and spare space are organized in redundancy
	     groups and	distributed evenly over	all of the devices.

	     This feature becomes active when creating a pool which uses the
	     draid vdev	type, or when adding a new draid vdev to an existing
	     pool.

     edonr
	     GUID		   org.illumos:edonr
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature enables the use of the Edon-R	hash algorithm for
	     checksum, including for nopwrite (if compression is also enabled,
	     an	overwrite of a block whose checksum matches the	data being
	     written will be ignored).	In an abundance	of caution, Edon-R re-
	     quires verification when used with	dedup: zfs set
	     dedup=edonr,verify	(see zfs-set(8)).

	     Edon-R is a very high-performance hash algorithm that was part of
	     the NIST SHA-3 competition.  It provides extremely	high hash per-
	     formance (over 350% faster	than SHA-256), but was not selected
	     because of	its unsuitability as a general purpose secure hash al-
	     gorithm.  This implementation utilizes the	new salted checksum-
	     ming functionality	in ZFS,	which means that the checksum is pre-
	     seeded with a secret 256-bit random key (stored on	the pool) be-
	     fore being	fed the	data block to be checksummed.  Thus the	pro-
	     duced checksums are unique	to a given pool, preventing hash col-
	     lision attacks on systems with dedup.

	     When the edonr feature is set to enabled, the administrator can
	     turn on the edonr checksum	on any dataset using zfs set
	     checksum=edonr dset (see zfs-set(8)).  This feature becomes
	     active once a checksum property has been set to edonr, and	will
	     return to being enabled once all filesystems that have ever had
	     their checksum set	to edonr are destroyed.

	     FreeBSD does not support the edonr	feature.

     embedded_data
	     GUID		   com.delphix:embedded_data
	     READ-ONLY COMPATIBLE  no

	     This feature improves the performance and compression ratio of
	     highly-compressible blocks.  Blocks whose contents	can compress
	     to	112 bytes or smaller can take advantage	of this	feature.

	     When this feature is enabled, the contents	of highly-compressible
	     blocks are	stored in the block "pointer" itself (a	misnomer in
	     this case,	as it contains the compressed data, rather than	a
	     pointer to	its location on	disk).	Thus the space of the block
	     (one sector, typically 512B or 4kB) is saved, and no additional
	     I/O is needed to read and write the data block.  This feature
	     becomes active as soon as it is enabled and will never return to
	     being enabled.

     empty_bpobj
	     GUID		   com.delphix:empty_bpobj
	     READ-ONLY COMPATIBLE  yes

	     This feature increases the	performance of creating	and using a
	     large number of snapshots of a single filesystem or volume, and
	     also reduces the disk space required.

	     When there	are many snapshots, each snapshot uses many Block
	     Pointer Objects (bpobjs) to track blocks associated with that
	     snapshot.	However, in common use cases, most of these bpobjs are
	     empty.  This feature allows us to create each bpobj on-demand,
	     thus eliminating the empty	bpobjs.

	     This feature is active while there	are any	filesystems, volumes,
	     or	snapshots which	were created after enabling this feature.

     enabled_txg
	     GUID		   com.delphix:enabled_txg
	     READ-ONLY COMPATIBLE  yes

	     Once this feature is enabled, ZFS records the transaction group
	     number in which new features are enabled.	This has no user-visi-
	     ble impact, but other features may	depend on this feature.

	     This feature becomes active
	      as soon as it is enabled and will	never return to	being enabled.

     encryption
	     GUID		   com.datto:encryption
	     DEPENDENCIES	   bookmark_v2,	extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature enables the creation and management of natively en-
	     crypted datasets.

	     This feature becomes active when an encrypted dataset is created
	     and will be returned to the enabled state when all	datasets that
	     use this feature are destroyed.

     extensible_dataset
	     GUID		   com.delphix:extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature allows more flexible use of internal ZFS data	struc-
	     tures, and	exists for other features to depend on.

	     This feature will be active when the first	dependent feature uses
	     it, and will be returned to the enabled state when	all datasets
	     that use this feature are destroyed.

     filesystem_limits
	     GUID		   com.joyent:filesystem_limits
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  yes

	     This feature enables filesystem and snapshot limits.  These lim-
	     its can be	used to	control	how many filesystems and/or snapshots
	     can be created at the point in the	tree on	which the limits are
	     set.

	     This feature is active once either	of the limit properties	has
	     been set on a dataset.  Once activated the	feature	is never deac-
	     tivated.

     hole_birth
	     GUID		   com.delphix:hole_birth
	     DEPENDENCIES	   enabled_txg
	     READ-ONLY COMPATIBLE  no

	     This feature has/had bugs,	the result of which is that, if	you do
	     a zfs send	-i (or -R, since it uses -i) from an affected dataset,
	     the receiving party will not see any checksum or other errors,
	     but the resulting destination snapshot will not match the source.
	     Its use by	zfs send -i has	been disabled by default (see
	     send_holes_without_birth_time in zfs(4)).

	     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.

	     An	incremental send stream	from snapshot A	to snapshot B contains
	     information about every block that	changed	between	A and B.
	     Blocks which did not change between those snapshots can be	iden-
	     tified and	omitted	from the stream	using a	piece of metadata
	     called the	"block birth time", but	birth times are	not recorded
	     for holes (blocks filled only with	zeroes).  Since	holes created
	     after A cannot be distinguished from holes	created	before A, in-
	     formation about every hole	in the entire filesystem or zvol is
	     included in the send stream.

	     For workloads where holes are rare	this is	not a problem.	How-
	     ever, when	incrementally replicating filesystems or zvols with
	     many holes	(for example a zvol formatted with another filesystem)
	     a lot of time will	be spent sending and receiving unnecessary in-
	     formation about holes that	already	exist on the receiving side.

	     Once the hole_birth feature has been enabled the block birth
	     times of all new holes will be recorded.  Incremental sends be-
	     tween snapshots created after this	feature	is enabled will	use
	     this new metadata to avoid	sending	information about holes	that
	     already exist on the receiving side.

	     This feature becomes active as soon as it is enabled and will
	     never return to being enabled.

     large_blocks
	     GUID		   org.open-zfs:large_blocks
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature allows the record size on a dataset to be set	larger
	     than 128kB.

	     This feature becomes active once a	dataset	contains a file	with a
	     block size	larger than 128kB, and will return to being enabled
	     once all filesystems that have ever had their recordsize larger
	     than 128kB	are destroyed.

     large_dnode
	     GUID		   org.zfsonlinux:large_dnode
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature allows the size of dnodes in a dataset to be set
	     larger than 512B.	This feature becomes active once a dataset
	     contains an object	with a dnode larger than 512B, which occurs as
	     a result of setting the dnodesize dataset property	to a value
	     other than	legacy.	 The feature will return to being enabled once
	     all filesystems that have ever contained a	dnode larger than 512B
	     are destroyed.  Large dnodes allow	more data to be	stored in the
	     bonus buffer, thus	potentially improving performance by avoiding
	     the use of	spill blocks.

     livelist
	     GUID		   com.delphix:livelist
	     READ-ONLY COMPATIBLE  yes

	     This feature allows clones	to be deleted faster than the tradi-
	     tional method when	a large	number of random/sparse	writes have
	     been made to the clone.  All blocks allocated and freed after a
	     clone is created are tracked by the the clone's livelist which is
	     referenced	during the deletion of the clone.  The feature is ac-
	     tivated when a clone is created and remains active	until all
	     clones have been destroyed.

     log_spacemap
	     GUID		   com.delphix:log_spacemap
	     DEPENDENCIES	   com.delphix:spacemap_v2
	     READ-ONLY COMPATIBLE  yes

	     This feature improves performance for heavily-fragmented pools,
	     especially	when workloads are heavy in random-writes.  It does so
	     by	logging	all the	metaslab changes on a single spacemap every
	     TXG instead of scattering multiple	writes to all the metaslab
	     spacemaps.

	     This feature becomes active as soon as it is enabled and will
	     never return to being enabled.

     lz4_compress
	     GUID		   org.illumos:lz4_compress
	     READ-ONLY COMPATIBLE  no

	     lz4 is a high-performance real-time compression algorithm that
	     features significantly faster compression and decompression as
	     well as a higher compression ratio	than the older lzjb compres-
	     sion.  Typically, lz4 compression is approximately	50% faster on
	     compressible data and 200%	faster on incompressible data than
	     lzjb.  It is also approximately 80% faster	on decompression,
	     while giving approximately	a 10% better compression ratio.

	     When the lz4_compress feature is set to enabled, the administra-
	     tor can turn on lz4 compression on	any dataset on the pool	using
	     the zfs-set(8) command.  All newly	written	metadata will be com-
	     pressed with the lz4 algorithm.

	     This feature becomes active as soon as it is enabled and will
	     never return to being enabled.

     multi_vdev_crash_dump
	     GUID		   com.joyent:multi_vdev_crash_dump
	     READ-ONLY COMPATIBLE  no

	     This feature allows a dump	device to be configured	with a pool
	     comprised of multiple vdevs.  Those vdevs may be arranged in any
	     mirrored or raidz configuration.

	     When the multi_vdev_crash_dump feature is set to enabled, the ad-
	     ministrator can use dumpadm(1M) to	configure a dump device	on a
	     pool comprised of multiple	vdevs.

	     Under FreeBSD and Linux this feature is unused, but registered
	     for compatibility.	 New pools created on these systems will have
	     the feature enabled but will never	transition to active, as this
	     functionality is not required for crash dump support.  Existing
	     pools where this feature is active	can be imported.

     obsolete_counts
	     GUID		   com.delphix:obsolete_counts
	     DEPENDENCIES	   device_removal
	     READ-ONLY COMPATIBLE  yes

	     This feature is an	enhancement of device_removal, which will over
	     time reduce the memory used to track removed devices.  When indi-
	     rect blocks are freed or remapped,	we note	that their part	of the
	     indirect mapping is "obsolete" a no longer	needed.

	     This feature becomes active when the zpool	remove command is used
	     on	a top-level vdev, and will never return	to being enabled.

     project_quota
	     GUID		   org.zfsonlinux:project_quota
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  yes

	     This feature allows administrators	to account the spaces and ob-
	     jects usage information against the project identifier (ID).

	     The project ID is an object-based attribute.  When	upgrading an
	     existing filesystem, objects without a project ID will be as-
	     signed a zero project ID.	When this feature is enabled, newly
	     created objects inherit their parent directories' project ID if
	     the parent's inherit flag is set (via chattr [+-]P	or zfs project
	     -s|-C).  Otherwise, the new object's project ID will be zero.  An
	     object's project ID can be	changed	at any time by the owner (or
	     privileged	user) via chattr -p prjid or zfs project -p prjid.

	     This feature will become active as	soon as	it is enabled and will
	     never return to being disabled.  Each filesystem will be upgraded
	     automatically when	remounted, or when a new file is created under
	     that filesystem. The upgrade can also be triggered	on filesystems
	     via zfs set version=current fs. The upgrade process runs in the
	     background	and may	take a while to	complete for filesystems
	     containing	large amounts of files.

     redaction_bookmarks
	     GUID		   com.delphix:redaction_bookmarks
	     DEPENDENCIES	   bookmarks, extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature enables the use of redacted zfs sends, which create
	     redaction bookmarks storing the list of blocks redacted by	the
	     send that created them.  For more information about redacted
	     sends, see	zfs-send(8).

     redacted_datasets
	     GUID		   com.delphix:redacted_datasets
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature enables the receiving	of redacted zfs	sendstreams.
	     which create redacted datasets when received.  These datasets are
	     missing some of their blocks, and so cannot be safely mounted,
	     and their contents	cannot be safely read.	For more information
	     about redacted receives, see zfs-send(8).

     resilver_defer
	     GUID		   com.datto:resilver_defer
	     READ-ONLY COMPATIBLE  yes

	     This feature allows ZFS to	postpone new resilvers if an existing
	     one is already in progress.  Without this feature,	any new	resil-
	     vers will cause the currently running one to be immediately
	     restarted from the	beginning.

	     This feature becomes active once a	resilver has been deferred,
	     and returns to being enabled when the deferred resilver begins.

     sha512
	     GUID		   org.illumos:sha512
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature enables the use of the SHA-512/256 truncated hash
	     algorithm (FIPS 180-4) for	checksum and dedup.  The native	64-bit
	     arithmetic	of SHA-512 provides an approximate 50% performance
	     boost over	SHA-256	on 64-bit hardware and is thus a good minimum-
	     change replacement	candidate for systems where hash performance
	     is	important, but these systems cannot for	whatever reason	uti-
	     lize the faster skein and edonr algorithms.

	     When the sha512 feature is	set to enabled,	the administrator can
	     turn on the sha512	checksum on any	dataset	using zfs set
	     checksum=sha512 dset (see zfs-set(8)).  This feature becomes
	     active once a checksum property has been set to sha512, and will
	     return to being enabled once all filesystems that have ever had
	     their checksum set	to sha512 are destroyed.

     skein
	     GUID		   org.illumos:skein
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     This feature enables the use of the Skein hash algorithm for
	     checksum and dedup.  Skein	is a high-performance secure hash al-
	     gorithm that was a	finalist in the	NIST SHA-3 competition.	 It
	     provides a	very high security margin and high performance on
	     64-bit hardware (80% faster than SHA-256).	 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 key	(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.

	     When the skein feature is set to enabled, the administrator can
	     turn on the skein checksum	on any dataset using zfs set
	     checksum=skein dset (see zfs-set(8)).  This feature becomes
	     active once a checksum property has been set to skein, and	will
	     return to being enabled once all filesystems that have ever had
	     their checksum set	to skein are destroyed.

     spacemap_histogram
	     GUID		   com.delphix:spacemap_histogram
	     READ-ONLY COMPATIBLE  yes

	     This features allows ZFS to maintain more information about how
	     free space	is organized within the	pool.  If this feature is
	     enabled, it will be activated when	a new space map	object is cre-
	     ated, or an existing space	map is upgraded	to the new format, and
	     never returns back	to being enabled.

     spacemap_v2
	     GUID		   com.delphix:spacemap_v2
	     READ-ONLY COMPATIBLE  yes

	     This feature enables the use of the new space map encoding	which
	     consists of two words (instead of one) whenever it	is advanta-
	     geous.  The new encoding allows space maps	to represent large re-
	     gions of space more efficiently on-disk while also	increasing
	     their maximum addressable offset.

	     This feature becomes active once it is enabled, and never returns
	     back to being enabled.

     userobj_accounting
	     GUID		   org.zfsonlinux:userobj_accounting
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  yes

	     This feature allows administrators	to account the object usage
	     information by user and group.

	     This feature becomes active as soon as it is enabled and will
	     never return to being enabled.  Each filesystem will be upgraded
	     automatically when	remounted, or when a new file is created under
	     that filesystem. The upgrade can also be triggered	on filesystems
	     via zfs set version=current fs. The upgrade process runs in the
	     background	and may	take a while to	complete for filesystems
	     containing	large amounts of files.

     zpool_checkpoint
	     GUID		   com.delphix:zpool_checkpoint
	     READ-ONLY COMPATIBLE  yes

	     This feature enables the zpool checkpoint command that can	check-
	     point the state of	the pool at the	time it	was issued and later
	     rewind back to it or discard it.

	     This feature becomes active when the zpool	checkpoint command is
	     used to checkpoint	the pool.  The feature will only return	back
	     to	being enabled when the pool is rewound or the checkpoint has
	     been discarded.

     zstd_compress
	     GUID		   org.freebsd:zstd_compress
	     DEPENDENCIES	   extensible_dataset
	     READ-ONLY COMPATIBLE  no

	     zstd is a high-performance	compression algorithm that features a
	     combination of high compression ratios and	high speed.  Compared
	     to	gzip, zstd offers slightly better compression at much higher
	     speeds.  Compared to lz4, zstd offers much	better compression
	     while being only modestly slower.	Typically, zstd	compression
	     speed ranges from 250 to 500 MB/s per thread and decompression
	     speed is over 1 GB/s per thread.

	     When the zstd feature is set to enabled, the administrator	can
	     turn on zstd compression of any dataset using zfs set
	     compress=zstd dset	(see zfs-set(8)).  This	feature	becomes	active
	     once a compress property has been set to zstd, and	will return to
	     being enabled once	all filesystems	that have ever had their
	     compress property set to zstd are destroyed.

SEE ALSO
     zpool(8)

FreeBSD	13.0			 May 31, 2021			  FreeBSD 13.0

NAME | DESCRIPTION | FEATURES | SEE ALSO

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