Post #2382402

2026-05-06 21:06 UTC

@grumpybozo@toad.social @zwol@masto.hackers.town @djfiander@code4lib.social @b0rk@social.jvns.ca generally, scrub does everything that fsck does and more. You can offline your pool if you want, but it works fine live. Most often, folks lose data because they don't bother to scrub.

Replies (2)

@zwol@masto.hackers.town 2026-05-06 21:20

@mwl@io.mwl.io @grumpybozo@toad.social @djfiander@code4lib.social @b0rk@social.jvns.ca zfs scrub does not validate or correct the on-disk data structure, it only checks the block checksums. That's what I mean by "doesn't have a *real* fsck." The data loss I experienced was due to a buggy migration of the on-disk data structure. All the block checksums validated, but files became inaccessible. Scrub did nothing. A real fsck might have dumped a bunch of stuff into lost+found, but that would've been enough to avoid having to restore from backup.

Open ##2382405
@mdione@en.osm.town 2026-05-07 12:52

@mwl@io.mwl.io @grumpybozo@toad.social @zwol@masto.hackers.town @djfiander@code4lib.social @b0rk@social.jvns.ca I wonder what scrub does, then, and why the fs code does not do it while doing the ops (probably for speed?), and how this is better than running fsck the the fs code finds inconsistency errors. I guess I should buy ZFS Mastery?

Open ##2382406