Before You Run ZFS Rewrite...

ZFS rewrite is a new feature that allows rewriting data in place after pool expansion, metadata changes, or parameter adjustments. While useful for avoiding data dumps, it has critical caveats: rewriting blocks doubles storage usage when snapshots exist, affects ZFS send operations, and doesn't support the preserve birth time flag in TrueNAS 25.10. The command can be stopped and restarted but doesn't resume from where it left off. It maintains file permissions and follows copy-on-write principles, minimizing data loss risk despite being write-intensive.