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
0.6.5.110.7.130.8.62.0.72.1.9master12.1.012.2.0mastermaster9.3main4.0.5-FP5.3masterr151042r151044master2.0.12.1.02.1.0-rc4master
org.zfsonlinux:allocation_classesyesnonoyesyesyesyesnoyesyesyesnononononoyesyesyesyesyesyesyes
com.delphix:async_destroyyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
org.openzfs:blake3nonononononoyesnononononononononononononononono
com.fudosecurity:block_cloningyesnononononoyesnononononononononononononononono
com.datto:bookmark_v2nononoyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyesyes
com.delphix:bookmark_writtennonononoyesyesyesnonononononononononononoyesyesyesyes
com.delphix:bookmarksyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:class_of_storageyesnonononononononononononoyesyesyesnonononononono
org.openzfs:device_rebuildyesnononoyesyesyesnonononononononononononoyesyesyesyes
com.delphix:device_removalnononoyesyesyesyesyesyesyesyesnononoyesyesyesyesyesyesyesyesyes
org.openzfs:draidnononononoyesyesnonononononononononononoyesyesyesyes
org.illumos:edonrnoyes1yes1yes1yes1yes1yesnonoyesyesnononoyesyesyesyesyesyesyesyesyes
com.delphix:embedded_datanoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
com.delphix:empty_bpobjyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:enabled_txgyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.datto:encryptionnononoyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyesyes
com.delphix:extensible_datasetnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.joyent:filesystem_limitsyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:head_errlognonononononoyesnononononononononononononononono
com.delphix:hole_birthnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
org.open-zfs:large_blocksnoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
org.zfsonlinux:large_dnodenonoyesyesyesyesyesnoyesyesyesnononononoyesyesyesyesyesyesyes
com.delphix:livelistyesnononoyesyesyesnonononononononononononoyesyesyesyes
com.delphix:log_spacemapyesnononoyesyesyesnonoyesyesnononononoyesyesyesyesyesyesyes
org.illumos:lz4_compressnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:meta_devicesyesnonononononononononononoyesyesyesnonononononono
com.joyent:multi_vdev_crash_dumpnonoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:obsolete_countsyesnonoyesyesyesyesyesyesyesyesnononoyesyesyesyesyesyesyesyesyes
org.zfsonlinux:project_quotayesnonoyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyesyes
com.delphix:redacted_datasetsnonononoyesyesyesnonononononononononononoyesyesyesyes
com.delphix:redaction_bookmarksnonononoyesyesyesnonononononononononononoyesyesyesyes
com.datto:resilver_deferyesnonoyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyesyes
org.illumos:sha512nonoyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
org.illumos:skeinnonoyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
com.delphix:spacemap_histogramyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:spacemap_v2yesnonoyesyesyesyesyesyesyesyesnononononoyesyesyesyesyesyesyes
org.zfsonlinux:userobj_accountingyesnoyesyesyesyesyesnonoyesyesnononononoyesyesyesyesyesyesyes
com.nexenta:vdev_propertiesyesnonononononononononononoyesyesyesnonononononono
com.nexenta:wbcnonononononononononononononoyesyesnonononononono
org.openzfs:zilsaxattryesnononononoyesnonoyesyesnonononononoyesyesnononono
com.delphix:zpool_checkpointyesnonoyesyesyesyesyesyesyesyesnononononoyesyesyesyesyesyesyes
org.freebsd:zstd_compressnonononoyesyesyesnonononononononononononoyesyesyesyes

Table generates by parsing manpages for feature flags, and is entirely dependent on good, accurate documentation.
Last updated on 2023-03-25T20:00:16.959410Z using compatibility_matrix.py.