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
0.6.5.110.7.130.8.62.0.52.1.0master11.4.012.1.012.2.0mastermaster9.2main4.0.5-FP5.3masterr151036r151038master1.9.21.9.31.9.4master
org.zfsonlinux:allocation_classesyesnonoyesyesyesyesnonoyesyesyesnononononoyesyesyesyesyesyesyes
com.delphix:async_destroyyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.datto:bookmark_v2nononoyesyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
com.delphix:bookmark_writtennonononoyesyesyesnonononononononononononononononono
com.delphix:bookmarksyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:class_of_storageyesnononononononononononononoyesyesyesnonononononono
org.openzfs:device_rebuildyesnononoyesyesyesnonononononononononononononononono
com.delphix:device_removalnononoyesyesyesyesyesyesyesyesyesnononoyesyesyesyesyesyesyesyesyes
org.openzfs:draidnononononoyesyesnonononononononononononononononono
org.illumos:edonrnonoyesyesyesyesyesnononoyesyesnononoyesyesyesyesyesyesyesyesyes
com.delphix:embedded_datanoyesyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
com.delphix:empty_bpobjyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:enabled_txgyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.datto:encryptionnononoyesyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
com.delphix:extensible_datasetnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.joyent:filesystem_limitsyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:hole_birthnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
org.open-zfs:large_blocksnoyesyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
org.zfsonlinux:large_dnodenonoyesyesyesyesyesnonoyesyesyesnononononoyesyesyesyesyesyesyes
com.delphix:livelistyesnononoyesyesyesnonononononononononononononononono
com.delphix:log_spacemapyesnononoyesyesyesnononoyesyesnononononoyesyesyesnononono
org.illumos:lz4_compressnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:meta_devicesyesnononononononononononononoyesyesyesnonononononono
com.joyent:multi_vdev_crash_dumpnonoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:obsolete_countsyesnonoyesyesyesyesyesyesyesyesyesnononoyesyesyesyesyesyesyesyesyes
org.zfsonlinux:project_quotayesnonoyesyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
com.delphix:redacted_datasetsnonononoyesyesyesnonononononononononononononononono
com.delphix:redaction_bookmarksnonononoyesyesyesnonononononononononononononononono
com.datto:resilver_deferyesnonoyesyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
org.illumos:sha512nonoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
org.illumos:skeinnonoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
com.delphix:spacemap_histogramyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:spacemap_v2yesnonoyesyesyesyesyesyesyesyesyesnononononoyesyesyesyesyesyesyes
org.zfsonlinux:userobj_accountingyesnoyesyesyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
com.nexenta:vdev_propertiesyesnononononononononononononoyesyesyesnonononononono
com.nexenta:wbcnononononononononononononononoyesyesnonononononono
com.delphix:zpool_checkpointyesnonoyesyesyesyesyesyesyesyesyesnononononoyesyesyesyesyesyesyes
org.freebsd:zstd_compressnonononoyesyesyesnonononononononononononononononono

Table generates by parsing manpages for feature flags, and is entirely dependent on good, accurate documentation.
Last updated on 2021-09-14T08:13:42.289170Z using compatibility_matrix.py.