The ZFS on-disk format

The last numbered version of the ZFS on-disk format is v28. Use of this version in OpenZFS guarantees compatibility between Solaris ZFS and OpenZFS. As Oracle’s code is no longer open source, OpenZFS is not compatible with Solaris ZFS pools beyond v28.


Version numbering was unsuitable for the distributed development of OpenZFS: 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 both independent and inter-dependent format changes.

Feature flags are implemented by artificially rolling the pool version to v5000 to avoid any conflicts with Oracle’s version.

The project tracks and documents the availability of each known OpenZFS feature by parsing each project’s man pages.