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
0.6.5.110.7.130.8.62.0.72.1.5master12.1.012.2.0mastermaster9.2main4.0.5-FP5.3masterr151040master2.0.12.1.02.1.0-rc4master
org.zfsonlinux:allocation_classesyesnonoyesyesyesyesnoyesyesyesnononononoyesyesyesyesyesyes
com.delphix:async_destroyyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
org.openzfs:blake3nonononononoyesnonononononononononononononono
com.datto:bookmark_v2nononoyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyes
com.delphix:bookmark_writtennonononoyesyesyesnononononononononononoyesyesyesyes
com.delphix:bookmarksyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:class_of_storageyesnonononononononononononoyesyesyesnononononono
org.openzfs:device_rebuildyesnononoyesyesyesnononononononononononoyesyesyesyes
com.delphix:device_removalnononoyesyesyesyesyesyesyesyesnononoyesyesyesyesyesyesyesyes
org.openzfs:draidnononononoyesyesnononononononononononoyesyesyesyes
org.illumos:edonrnonoyesyesyesyesyesnonoyesyesnononoyesyesyesyesyesyesyesyes
com.delphix:embedded_datanoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
com.delphix:empty_bpobjyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:enabled_txgyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.datto:encryptionnononoyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyes
com.delphix:extensible_datasetnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.joyent:filesystem_limitsyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:head_errlognonononononoyesnonononononononononononononono
com.delphix:hole_birthnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
org.open-zfs:large_blocksnoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
org.zfsonlinux:large_dnodenonoyesyesyesyesyesnoyesyesyesnononononoyesyesyesyesyesyes
com.delphix:livelistyesnononoyesyesyesnononononononononononoyesyesyesyes
com.delphix:log_spacemapyesnononoyesyesyesnonoyesyesnononononoyesyesyesyesyesyes
org.illumos:lz4_compressnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:meta_devicesyesnonononononononononononoyesyesyesnononononono
com.joyent:multi_vdev_crash_dumpnonoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:obsolete_countsyesnonoyesyesyesyesyesyesyesyesnononoyesyesyesyesyesyesyesyes
org.zfsonlinux:project_quotayesnonoyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyes
com.delphix:redacted_datasetsnonononoyesyesyesnononononononononononoyesyesyesyes
com.delphix:redaction_bookmarksnonononoyesyesyesnononononononononononoyesyesyesyes
com.datto:resilver_deferyesnonoyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyes
org.illumos:sha512nonoyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
org.illumos:skeinnonoyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyes
com.delphix:spacemap_histogramyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:spacemap_v2yesnonoyesyesyesyesyesyesyesyesnononononoyesyesyesyesyesyes
org.zfsonlinux:userobj_accountingyesnoyesyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyes
com.nexenta:vdev_propertiesyesnonononononononononononoyesyesyesnononononono
com.nexenta:wbcnonononononononononononononoyesyesnononononono
org.openzfs:zilsaxattryesnononononoyesnonoyesyesnonononononoyesnononono
com.delphix:zpool_checkpointyesnonoyesyesyesyesyesyesyesyesnononononoyesyesyesyesyesyes
org.freebsd:zstd_compressnonononoyesyesyesnononononononononononoyesyesyesyes

Table generates by parsing manpages for feature flags, and is entirely dependent on good, accurate documentation.
Last updated on 2022-07-06T06:29:31.441145Z using compatibility_matrix.py.