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Raidz Expansion Feature
- throw0101a 5y agoTL; DR: Start with six-wide RAIDz2 vdev. In this vdev, records are mostly written in six-wide chunks—so a 128KiB record is written in four 32KiB data chunks plus two 32KiB parity chunks. Now use zpool attach and Matt Ahrens' new code to expand my six-wide RAIDz2 vdev to a ten-wide RAIDz2 vdev. Full-size stripes will now consist of eight data chunks and two parity chunks. What zpool attach does not do is reshape existing records/blocks, which are still in six-wide stripes. Since ZFS is a copy-on-write file system, rewritten blocks will be "the new normal" with eight data chunks and two parity chunks. Also: if you write a 4K file, that's a single sector—so instead, that small file is written as a narrower stripe, thanks to ZFS' variable stripe width. This narrow stripe is only three disks wide—one data chunk, plus two parity chunks. * From: https://old.reddit.com/r/zfs/comments/nx88vr/raidz_expansion_feature_pull_request/ https://old.reddit.com/r/zfs/comments/nx88vr/raidz_expansion...