'\" te
-.\" Copyright (c) 2012 by Delphix. All rights reserved.
+.\" Copyright (c) 2013, 2017 by Delphix. All rights reserved.
+.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+.\" Copyright (c) 2014, Joyent, Inc. All rights reserved.
.\" 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 ZPOOL-FEATURES 5 "Mar 16, 2012"
+.TH ZPOOL-FEATURES 5 "Jun 8, 2018"
.SH NAME
zpool\-features \- ZFS pool feature descriptions
.SH DESCRIPTION
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
28). To enable a feature on a pool use the \fBupgrade\fR subcommand of the
-\fBzpool\fR(1M) command, or set the \fBfeature@\fR\fIfeature_name\fR property
+\fBzpool\fR(8) command, or set the \fBfeature@\fR\fIfeature_name\fR property
to \fBenabled\fR.
.sp
.LP
software's ability to read from the pool. These features are referred 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
-\fBreadonly\fR property during import (see \fBzpool\fR(1M) for details on
+\fBreadonly\fR property during import (see \fBzpool\fR(8) for details on
importing pools).
.SS "Unsupported features"
.sp
or snapshots which were created after enabling this feature.
.RE
+.sp
+.ne 2
+.na
+\fB\fBfilesystem_limits\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+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
+the tree on which the limits are set.
+
+This feature is \fBactive\fR once either of the limit properties has been
+set on a dataset. Once activated the feature is never deactivated.
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBlz4_compress\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.illumos:lz4_compress
+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
+higher compression ratio than the older \fBlzjb\fR compression.
+Typically, \fBlz4\fR compression is approximately 50% faster on
+compressible data and 200% faster on incompressible data than
+\fBlzjb\fR. It is also approximately 80% faster on decompression, while
+giving approximately 10% better compression ratio.
+
+When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the
+administrator can turn on \fBlz4\fR compression on any dataset on the
+pool using the \fBzfs\fR(8) command. Please note that doing so will
+immediately activate the \fBlz4_compress\fR feature on the underlying
+pool using the \fBzfs\fR(1M) command. Also, all newly written metadata
+will be compressed with \fBlz4\fR algorithm. Since this feature is not
+read-only compatible, this operation will render the pool unimportable
+on systems without support for the \fBlz4_compress\fR feature.
+
+Booting off of \fBlz4\fR-compressed root pools is supported.
+
+This feature becomes \fBactive\fR as soon as it is enabled and will
+never return to being \fBenabled\fB.
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBspacemap_histogram\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID com.delphix:spacemap_histogram
+READ\-ONLY COMPATIBLE yes
+DEPENDENCIES none
+.TE
+
+This features allows ZFS to maintain more information about how free space
+is organized within the pool. If this feature is \fBenabled\fR, ZFS will
+set this feature to \fBactive\fR when a new space map object is created or
+an existing space map is upgraded to the new format. Once the feature is
+\fBactive\fR, it will remain in that state until the pool is destroyed.
+
+.RE
+
+.sp
+.ne 2
+.na
+\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
+of multiple vdevs. Those vdevs may be arranged in any mirrored or raidz
+configuration.
+
+When the \fBmulti_vdev_crash_dump\fR feature is set to \fBenabled\fR,
+the administrator can use the \fBdumpadm\fR(1M) command to configure a
+dump device on a pool comprised of multiple vdevs.
+
+Under Linux this feature is registered for compatibility but not used.
+New pools created under Linux will have the feature \fBenabled\fR but
+will never transition to \fB\fBactive\fR. This functionality is not
+required in order to support crash dumps under Linux. Existing pools
+where this feature is \fB\fBactive\fR can be imported.
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBextensible_dataset\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID com.delphix:extensible_dataset
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES none
+.TE
+
+This feature allows more flexible use of internal ZFS data structures,
+and exists for other features to depend on.
+
+This feature will be \fBactive\fR when the first dependent feature uses it,
+and will be returned to the \fBenabled\fR state when all datasets that use
+this feature are destroyed.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBbookmarks\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID com.delphix:bookmarks
+READ\-ONLY COMPATIBLE yes
+DEPENDENCIES extensible_dataset
+.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
+\fBzfs list -t bookmark -r \fIpoolname\fR\fR.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBenabled_txg\fR\fR
+.ad
+.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
+in which new features are enabled. This has no user-visible impact,
+but other features may depend on this feature.
+
+This feature becomes \fBactive\fR as soon as it is enabled and will
+never return to being \fBenabled\fB.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBhole_birth\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID com.delphix:hole_birth
+READ\-ONLY COMPATIBLE no
+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.
+
+An incremental send stream from snapshot \fBA\fR to snapshot \fBB\fR
+contains information about every block that changed between \fBA\fR and
+\fBB\fR. Blocks which did not change between those snapshots can be
+identified 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 \fBA\fR cannot be
+distinguished from holes created before \fBA\fR, information 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. However, 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 information about holes that
+already exist on the receiving side.
+
+Once the \fBhole_birth\fR 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
+sending information about holes that already exist on the receiving side.
+
+This feature becomes \fBactive\fR as soon as it is enabled and will
+never return to being \fBenabled\fB.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBembedded_data\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID com.delphix:embedded_data
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES none
+.TE
+
+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 512 bytes or 4KB) is saved,
+and no additional i/o is needed to read and write the data block.
+
+This feature becomes \fBactive\fR as soon as it is enabled and will
+never return to being \fBenabled\fR.
+
+.RE
+.sp
+.ne 2
+.na
+\fB\fBdevice_removal\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID com.delphix:device_removal
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES none
+.TE
+
+This feature enables the "zpool remove" subcommand to remove top-level
+vdevs, evacuating them to reduce the total size of the pool.
+
+This feature becomes \fBactive\fR when the "zpool remove" command is used
+on a top-level vdev, and will never return to being \fBenabled\fR.
+
+.RE
+.sp
+.ne 2
+.na
+\fB\fBobsolete_counts\fR\fR
+.ad
+.RS 4n
+.TS
+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
+reduce the memory used to track removed devices. When indirect blocks
+are freed or remapped, we note that their part of the indirect mapping
+is "obsolete", i.e. no longer needed.
+
+This feature becomes \fBactive\fR when the "zpool remove" command is
+used on a top-level vdev, and will never return to being \fBenabled\fR.
+
+.RE
+.sp
+.ne 2
+.na
+\fB\fBzpool_checkpoint\fR\fR
+.ad
+.RS 4n
+.TS
+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
+consists of two words (instead of one) whenever it is advantageous.
+The new encoding allows space maps to represent large regions of
+space more efficiently on-disk while also increasing their maximum
+addressable offset.
+
+This feature becomes \fBactive\fR once it is \fBenabled\fR, and never
+returns back to being \fBenabled\fR.
+
+.RE
+.sp
+.ne 2
+.na
+\fB\fBlarge_blocks\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.open-zfs:large_block
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES extensible_dataset
+.TE
+
+The \fBlarge_block\fR feature allows the record size on a dataset to be
+set larger than 128KB.
+
+This feature becomes \fBactive\fR once a dataset contains a file with
+a block size larger than 128KB, and will return to being \fBenabled\fR once all
+filesystems that have ever had their recordsize larger than 128KB are destroyed.
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBlarge_dnode\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.zfsonlinux:large_dnode
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES extensible_dataset
+.TE
+
+The \fBlarge_dnode\fR feature allows the size of dnodes in a dataset to be
+set larger than 512B.
+
+This feature becomes \fBactive\fR once a dataset contains an object with
+a dnode larger than 512B, which occurs as a result of setting the
+\fBdnodesize\fR dataset property to a value other than \fBlegacy\fR. The
+feature will return to being \fBenabled\fR 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.
+.RE
+
+\fB\fBsha512\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.illumos:sha512
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES extensible_dataset
+.TE
+
+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 utilize the faster \fBskein\fR and
+\fBedonr\fR algorithms.
+
+When the \fBsha512\fR feature is set to \fBenabled\fR, the administrator
+can turn on the \fBsha512\fR checksum on any dataset using the
+\fBzfs set checksum=sha512\fR(1M) command. This feature becomes
+\fBactive\fR once a \fBchecksum\fR property has been set to \fBsha512\fR,
+and will return to being \fBenabled\fR once all filesystems that have
+ever had their checksum set to \fBsha512\fR are destroyed.
+
+Booting off of pools utilizing SHA-512/256 is supported.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBskein\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.illumos:skein
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES extensible_dataset
+.TE
+
+This feature enables the use of the Skein hash algorithm for checksum
+and dedup. Skein is a high-performance secure hash algorithm 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 \fBskein\fR feature is set to \fBenabled\fR, the administrator
+can turn on the \fBskein\fR checksum on any dataset using the
+\fBzfs set checksum=skein\fR(1M) command. This feature becomes
+\fBactive\fR once a \fBchecksum\fR property has been set to \fBskein\fR,
+and will return to being \fBenabled\fR once all filesystems that have
+ever had their checksum set to \fBskein\fR are destroyed.
+
+Booting off of pools using \fBskein\fR is supported.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBedonr\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.illumos:edonr
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES extensible_dataset
+.TE
+
+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 can not be used with dedup
+(without verification).
+
+Edon-R is a very high-performance hash algorithm that was part
+of the NIST SHA-3 competition. It provides extremely high hash
+performance (over 350% faster than SHA-256), but was not selected
+because of its unsuitability as a general purpose secure hash algorithm.
+This implementation 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.
+
+When the \fBedonr\fR feature is set to \fBenabled\fR, the administrator
+can turn on the \fBedonr\fR checksum on any dataset using the
+\fBzfs set checksum=edonr\fR(1M) command. This feature becomes
+\fBactive\fR once a \fBchecksum\fR property has been set to \fBedonr\fR,
+and will return to being \fBenabled\fR once all filesystems that have
+ever had their checksum set to \fBedonr\fR are destroyed.
+
+Booting off of pools using \fBedonr\fR is supported.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBuserobj_accounting\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.zfsonlinux:userobj_accounting
+READ\-ONLY COMPATIBLE yes
+DEPENDENCIES extensible_dataset
+.TE
+
+This feature allows administrators to account the object usage information
+by user and group.
+
+This feature becomes \fBactive\fR as soon as it is enabled and will never
+return to being \fBenabled\fR. Each filesystem will be upgraded automatically
+when remounted, or when new files are created under that filesystem.
+The upgrade can also be started manually on filesystems by running
+`zfs set version=current <pool/fs>`. The upgrade process runs in the background
+and may take a while to complete for filesystems containing a large number of
+files.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBencryption\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID com.datto:encryption
+READ\-ONLY COMPATIBLE no
+DEPENDENCIES extensible_dataset
+.TE
+
+This feature enables the creation and management of natively encrypted datasets.
+
+This feature becomes \fBactive\fR when an encrypted dataset is created and will
+be returned to the \fBenabled\fR state when all datasets that use this feature
+are destroyed.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBproject_quota\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.zfsonlinux:project_quota
+READ\-ONLY COMPATIBLE yes
+DEPENDENCIES extensible_dataset
+.TE
+
+This feature allows administrators to account the spaces and objects usage
+information against the project identifier (ID).
+
+The project ID is new object-based attribute. When upgrading an existing
+filesystem, object without project ID attribute will be assigned a zero
+project ID. After this feature is enabled, newly created object will inherit
+its parent directory's project ID if the parent inherit flag is set (via
+\fBchattr +/-P\fR or \fBzfs project [-s|-C]\fR). Otherwise, the new object's
+project ID will be set as zero. An object's project ID can be changed at
+anytime by the owner (or privileged user) via \fBchattr -p $prjid\fR or
+\fBzfs project -p $prjid\fR.
+
+This feature will become \fBactive\fR as soon as it is enabled and will never
+return to being \fBdisabled\fR. Each filesystem will be upgraded automatically
+when remounted or when new file is created under that filesystem. The upgrade
+can also be triggered on filesystems via `zfs set version=current <pool/fs>`.
+The upgrade process runs in the background and may take a while to complete
+for the filesystems containing a large number of files.
+
+.RE
+.sp
+.ne 2
+.na
+\fB\fBresilver_defer\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID com.datto:resilver_defer
+READ\-ONLY COMPATIBLE yes
+DEPENDENCIES none
+.TE
+
+This feature allows zfs to postpone new resilvers if an existing one is already
+in progress. Without this feature, any new resilvers will cause the currently
+running one to be immediately restarted from the beginning.
+
+This feature becomes \fBactive\fR once a resilver has been defered, and returns
+to being \fBenabled\fR when the defered resilver begins.
+
+.RE
+
+.sp
+.ne 2
+.na
+\fB\fBallocation_classes\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID org.zfsonlinux:allocation_classes
+READ\-ONLY COMPATIBLE yes
+DEPENDENCIES none
+.TE
+
+This feature enables support for separate allocation classes.
+
+This feature becomes \fBactive\fR when a dedicated allocation class vdev
+(dedup or special) is created with zpool create or zpool add. With device
+removal, it can be returned to the \fBenabled\fR state if all the top-level
+vdevs from an allocation class are removed.
+
+.RE
+
.SH "SEE ALSO"
-\fBzpool\fR(1M)
+\fBzpool\fR(8)
projects / mirror_zfs.git / blobdiff