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(5) 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
0.6.5.110.7.130.8.62.0.1master11.4.012.1.012.2.0mastermaster9.1main4.0.5-FP5.3masterr151034r151036master1.9.21.9.31.9.4master
org.zfsonlinux:allocation_classesyesnonoyesyesyesnonoyesyesyesnononononoyesyesyesyesyesyesyes
com.delphix:async_destroyyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.datto:bookmark_v2nononoyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
com.delphix:bookmark_writtennonononoyesyesnonononononononononononononononono
com.delphix:bookmarksyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:class_of_storageyesnonononononononononononoyesyesyesnonononononono
org.openzfs:device_rebuildyesnononoyesyesnonononononononononononononononono
com.delphix:device_removalnononoyesyesyesyesyesyesyesyesnononoyesyesyesyesyesyesyesyesyes
org.openzfs:draidnononononoyesnonononononononononononononononono
org.illumos:edonrnonoyesyesyesyesnononoyesyesnononoyesyesyesyesyesyesyesyesyes
com.delphix:embedded_datanoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
com.delphix:empty_bpobjyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:enabled_txgyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.datto:encryptionnononoyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
com.delphix:extensible_datasetnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.joyent:filesystem_limitsyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:hole_birthnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
org.open-zfs:large_blocksnoyesyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
org.zfsonlinux:large_dnodenonoyesyesyesyesnonoyesyesyesnononononoyesyesyesyesyesyesyes
com.delphix:livelistyesnononoyesyesnonononononononononononononononono
com.delphix:log_spacemapyesnononoyesyesnononoyesyesnononononoyesyesyesnononono
org.illumos:lz4_compressnoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.nexenta:meta_devicesyesnonononononononononononoyesyesyesnonononononono
com.joyent:multi_vdev_crash_dumpnonoyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:obsolete_countsyesnonoyesyesyesyesyesyesyesyesnononoyesyesyesyesyesyesyesyesyes
org.zfsonlinux:project_quotayesnonoyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
com.delphix:redacted_datasetsnonononoyesyesnonononononononononononononononono
com.delphix:redaction_bookmarksnonononoyesyesnonononononononononononononononono
com.datto:resilver_deferyesnonoyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
org.illumos:sha512nonoyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
org.illumos:skeinnonoyesyesyesyesyesyesyesyesyesyesyesnoyesyesyesyesyesyesyesyesyes
com.delphix:spacemap_histogramyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes
com.delphix:spacemap_v2yesnonoyesyesyesyesyesyesyesyesnononononoyesyesyesyesyesyesyes
org.zfsonlinux:userobj_accountingyesnoyesyesyesyesnononoyesyesnononononoyesyesyesyesyesyesyes
com.nexenta:vdev_propertiesyesnonononononononononononoyesyesyesnonononononono
com.nexenta:wbcnonononononononononononononoyesyesnonononononono
com.delphix:zpool_checkpointyesnonoyesyesyesyesyesyesyesyesnononononoyesyesyesyesyesyesyes
org.freebsd:zstd_compressnonononoyesyesnonononononononononononononononono

Table generates by parsing manpages for feature flags, and is entirely dependent on good, accurate documentation.
Last updated on 2021-01-21T22:59:00.902893Z using compatibility_matrix.py.