On Friday 18 Sep 2015 19:30:49 Rich Freeman wrote: > On Fri, Sep 18, 2015 at 2:19 PM, Mick <michaelkintz...@gmail.com> wrote: > > On Friday 18 Sep 2015 19:15:50 Rich Freeman wrote: > >> On Fri, Sep 18, 2015 at 1:56 PM, Mick <michaelkintz...@gmail.com> wrote: > >> > On Friday 18 Sep 2015 17:16:54 Marc Joliet wrote: > >> >> On Friday 18 September 2015 10:31:01 Mick wrote: > >> >> >A couple of months ago the akonadi DB went sideways and kmail played > >> >> >up as a result. Again I was suspicious of btrfs, but neither the > >> >> >logs nor fsck showed up anything. > >> >> > >> >> I take it "btrfs scrub" didn't turn up anything, or is that what you > >> >> meant by fsck? > >> > > >> > Am I supposed to run scrub with I do not have a RAID running? I > >> > thought scrub was meant for comparing checksums between mirrored fs - > >> > have I got this wrong? > >> > >> You can actually run scrub on a non-raid btrfs setup. Btrfs will > >> report any errors that it detects (using the checksumming in the > >> filesystem), but it would not be able to fix errors unless you have it > >> storing redundant data somewhere (even on non-raid it still stores > >> redundant metadata by default, and you can choose to do this with data > >> as well which protects against block-level failures but not disk-level > >> failures, obviously). > >> > >> However, you'd have gotten the same errors in dmesg just trying to > >> read the files - btrfs checks the checksum on all file read > >> operations. That is a big part of the value of both btrfs and zfs. > > > > Ah! V interesting ... can I run scrub with mounted partitions, or do I > > have to do it from a LiveCD? > > I didn't check, but I suspect you can only run scrub on a mounted > partition. I also suspect that fsck probably has an option to do > something equivalent offline. > > You do get the error-detection anyway just by reading files, and if > you just ran find on your filesystem and catted every file you have to > /dev/null that would actually accomplish the same thing as long as > you're not in a redundant mode (simply reading all the files doesn't > guarantee that all copies of each file are checked). > > The main reason for doing a scrub is to detect latent issues, and if > you have redundancy that means you can auto-correct them today, rather > than discovering them a month from now when the drive containing the > only good copy fails. Even if you don't have redundancy maybe you > rotate your backups every 30 days and detecting the error might mean > having the ability to go back and restore a good copy of the file > before it is completely replaced with bad copies.
Thank you Rich, I ran 'btrfs scrub start /" and it found zero problems. dmesg and syslog clean too. -- Regards, Mick
signature.asc
Description: This is a digitally signed message part.
