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 FlagRead-Only
Compatible
OpenZFS (Linux, FreeBSD 13+)FreeBSD pre OpenZFSIllumosJoyentNetBSDNexentaOmniOS CEOpenZFS on OS X
0.6.5.110.7.130.8.62.0.72.1.162.2.72.3.1master12.1.012.2.0mastermaster4.0.5-FPmasterr151050r151052master2.2.22.2.32.3.0rc1main
org.zfsonlinux:allocation_classesyesnonoyesyesyesyesyesyesnoyesyesyesnonoyesyesyesyesyesyesyes
com.delphix:async_destroyyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
org.openzfs:blake3nonononononoyesyesyesnononononononononoyesyesyesyes
com.fudosecurity:block_cloningyesnononononoyesyesyesnononononononononoyesyesyesyes
com.datto:bookmark_v2nononoyesyesyesyesyesyesnonoyesyesnonoyesyesyesyesyesyesyes
com.delphix:bookmark_writtennonononoyesyesyesyesyesnononononononononoyesyesyesyes
com.delphix:bookmarksyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:class_of_storageyesnonononononononononononoyesyesnonononononono
org.openzfs:device_rebuildyesnononoyesyesyesyesyesnononononononononoyesyesyesyes
com.delphix:device_removalnononoyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
org.openzfs:draidnononononoyesyesyesyesnononononononononoyesyesyesyes
org.illumos:edonrnoyes1yes1yes1yes1yes1yes1yes1yesnonoyesyesnoyesyesyesyesyesyesyesyes
com.delphix:embedded_datanoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
com.delphix:empty_bpobjyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:enabled_txgyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.datto:encryptionnononoyesyesyesyesyesyesnonoyesyesnonoyesyesyesyesyesyesyes
com.delphix:extensible_datasetnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.klarasystems:fast_dedupyesnonononononoyesyesnononononononononononoyesyes
com.joyent:filesystem_limitsyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:head_errlognonononononoyesyesyesnononononononononoyesyesyesyes
com.delphix:hole_birthnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
org.open-zfs:large_blocksnoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
org.zfsonlinux:large_dnodenonoyesyesyesyesyesyesyesnoyesyesyesnonoyesyesyesyesyesyesyes
com.klarasystems:large_microzapyesnonononononoyesyesnononononononononononoyesyes
com.delphix:livelistyesnononoyesyesyesyesyesnononononononononoyesyesyesyes
com.delphix:log_spacemapyesnononoyesyesyesyesyesnonoyesyesnonoyesyesyesyesyesyesyes
org.zfsonlinux:longnamenononononononoyesyesnononononononononononoyesyes
org.illumos:lz4_compressnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:meta_devicesyesnonononononononononononoyesyesnonononononono
com.joyent:multi_vdev_crash_dumpnonoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:obsolete_countsyesnonoyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
org.zfsonlinux:project_quotayesnonoyesyesyesyesyesyesnonoyesyesnonoyesyesyesyesyesyesyes
org.openzfs:raidz_expansionnononononononoyesyesnononononononononoyesyesyesyes
com.delphix:redacted_datasetsnonononoyesyesyesyesyesnononononononononoyesyesyesyes
com.delphix:redaction_bookmarksnonononoyesyesyesyesyesnononononononononoyesyesyesyes
com.delphix:redaction_list_spillnononononononoyesyesnononononononononoyesyesyesyes
com.datto:resilver_deferyesnonoyesyesyesyesyesyesnonoyesyesnonoyesyesyesyesyesyesyes
org.illumos:sha512nonoyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
org.illumos:skeinnonoyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
com.delphix:spacemap_histogramyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:spacemap_v2yesnonoyesyesyesyesyesyesyesyesyesyesnonoyesyesyesyesyesyesyes
org.zfsonlinux:userobj_accountingyesnoyesyesyesyesyesyesyesnonoyesyesnonoyesyesyesyesyesyesyes
com.nexenta:vdev_propertiesyesnonononononononononononoyesyesnonononononono
com.klarasystems:vdev_zaps_v2nonononononoyesyesyesnononononononononoyesyesyesyes
com.nexenta:wbcnonononononononononononononoyesnonononononono
org.openzfs:zilsaxattryesnononononoyesyesyesnonoyesyesnonoyesyesyesyesyesyesyes
com.delphix:zpool_checkpointyesnonoyesyesyesyesyesyesyesyesyesyesnonoyesyesyesyesyesyesyes
org.freebsd:zstd_compressnonononoyesyesyesyesyesnononononononononoyesyesyesyes

Table generates by parsing manpages for feature flags, and is entirely dependent on good, accurate documentation.
Last updated on 2025-04-30T21:58:54.445146Z using compatibility_matrix.py.