Feature Flags

ZFS on-disk formats were originally versioned with a single number, which increased whenever the format changed. The numbered approach was suitable when development of ZFS was driven by a single organisation.

For distributed development of OpenZFS, version numbering was unsuitable. Any change to the number would have required agreement, across all implementations, of each change to the on-disk format.

OpenZFS feature flags – an alternative to traditional version numbering – allow a uniquely named pool property for each change to the on-disk format. This approach supports:

format changes that are independent
format changes that depend on each other.

Compatibility

Where all features that are used by a pool are supported by multiple implementations of OpenZFS, the on-disk format is portable across those implementations.

Features that are exclusive when enabled should be periodically ported to all distributions.

Reference materials

ZFS Feature Flags (Christopher Siden, 2012-01, in the Internet Archive Wayback Machine) in particular: “… Legacy version numbers still exist for pool versions 1-28 …”.

zpool-features(7) man page - OpenZFS

zpool-features (5) – illumos

Feature flags implementation per OS

ZFS Feature Matrix

Feature Flag	Read-Only Compatible	OpenZFS (Linux, FreeBSD 13+)									FreeBSD pre OpenZFS	Illumos	Joyent	NetBSD	Nexenta	OmniOS CE			OpenZFS on OS X
Feature Flag	Read-Only Compatible	0.6.5.11	0.7.13	0.8.6	2.0.7	2.1.16	2.2.10	2.3.8	2.4.3	master	12	master	master	main	master	r151056	r151058	master	2.3.1p1	2.3.1p2	2.4.1rc5	main
org.zfsonlinux:allocation_classes	yes	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
com.delphix:async_destroy	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
org.openzfs:blake3	no	no	no	no	no	no	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.fudosecurity:block_cloning	yes	no	no	no	no	no	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.truenas:block_cloning_endian	yes	no	no	no	no	no	no	no	yes	yes	no	no	no	no	no	no	no	no	no	no	yes	no
com.datto:bookmark_v2	no	no	no	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
com.delphix:bookmark_written	no	no	no	no	yes	yes	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:bookmarks	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.nexenta:class_of_storage	yes	no	no	no	no	no	no	no	no	no	no	no	no	no	yes	no	no	no	no	no	no	no
org.openzfs:device_rebuild	yes	no	no	no	yes	yes	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:device_removal	no	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	yes	yes	yes	yes	yes	yes
org.openzfs:draid	no	no	no	no	no	yes	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.seagate:draid_failure_domains	no	no	no	no	no	no	no	no	no	yes	no	no	no	no	no	no	no	no	no	no	no	no
com.klarasystems:dynamic_gang_header	no	no	no	no	no	no	no	no	yes	yes	no	no	no	no	no	no	no	no	no	no	yes	no
org.illumos:edonr	no	yes¹	yes¹	yes¹	yes¹	yes¹	yes	yes	yes	yes	no	yes	yes	no	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:embedded_data	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:empty_bpobj	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:enabled_txg	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.datto:encryption	no	no	no	yes	yes	yes	yes	yes	yes	yes	no	yes²	yes	no	no	yes	yes	yes	yes	yes	yes	yes
com.delphix:extensible_dataset	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.klarasystems:fast_dedup	yes	no	no	no	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.joyent:filesystem_limits	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:head_errlog	no	no	no	no	no	no	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:hole_birth	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
org.open-zfs:large_blocks	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
org.zfsonlinux:large_dnode	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
com.klarasystems:large_microzap	yes	no	no	no	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:livelist	yes	no	no	no	yes	yes	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:log_spacemap	yes	no	no	no	yes	yes	yes	yes	yes	yes	no	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
org.zfsonlinux:longname	no	no	no	no	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
org.illumos:lz4_compress	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.nexenta:meta_devices	yes	no	no	no	no	no	no	no	no	no	no	no	no	no	yes	no	no	no	no	no	no	no
com.joyent:multi_vdev_crash_dump	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:obsolete_counts	yes	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	yes	yes	yes	yes	yes	yes
com.truenas:physical_rewrite	yes	no	no	no	no	no	no	no	yes	yes	no	no	no	no	no	no	no	no	no	no	yes	no
org.zfsonlinux:project_quota	yes	no	no	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
org.openzfs:raidz_expansion	no	no	no	no	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:redacted_datasets	no	no	no	no	yes	yes	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:redaction_bookmarks	no	no	no	no	yes	yes	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:redaction_list_spill	no	no	no	no	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.datto:resilver_defer	yes	no	no	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
org.illumos:sha512	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
org.illumos:skein	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:spacemap_histogram	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:spacemap_v2	yes	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
org.zfsonlinux:userobj_accounting	yes	no	yes	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
com.nexenta:vdev_properties	yes	no	no	no	no	no	no	no	no	no	no	no	no	no	yes	no	no	no	no	no	no	no
com.klarasystems:vdev_zaps_v2	no	no	no	no	no	no	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.nexenta:wbc	no	no	no	no	no	no	no	no	no	no	no	no	no	no	yes	no	no	no	no	no	no	no
org.openzfs:zilsaxattr	yes	no	no	no	no	no	yes	yes	yes	yes	no	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
com.delphix:zpool_checkpoint	yes	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	no	yes	yes	yes	yes	yes	yes	yes
org.freebsd:zstd_compress	no	no	no	no	yes	yes	yes	yes	yes	yes	no	no	no	no	no	no	no	no	yes	yes	yes	yes

Notes:

Table generates by parsing manpages for feature flags, and is entirely dependent on good, accurate documentation.
Last updated on 2026-07-09T04:26:01.463841Z using compatibility_matrix.py.