On Wed, 29 Oct 2008 14:02:04 -0600
Joe Peterson <[EMAIL PROTECTED]> wrote:
> Chris Mason wrote:
> > On Tue, 2008-10-28 at 16:48 -0700, Stephen Hemminger wrote:
> >> I have a system with a pair of small/fast but unreliable scsi drives.
> >> I tried setting up a raid1 configuration and using it for builds.
> >> Using 2.6.26.7 and btrfs 0.16. When using ext3 (no raid) on same
> >> partition,
> >> the driver would recalibrate and log something an keep going. But with
> >> btrfs it doesn't recover and takes drive offline.
> >>
> >
> > Btrfs doesn't really take drives offline. In the future we'll notice
> > that a drive is returning all errors, but for now we'll probably just
> > keep beating on it.
>
> It can also detect when a bad checksum is returned or the drive returns an i/o
> error, right? Would the "all-zero" test be a heuristic in case neither of
> those
> happened (but I cannot imagine why the zeros would get by the checksum check)?
>
> > The IO error handling code in btrfs currently expects it'll be able to
> > find at least one good mirror. You're probably hitting some bad
> > conditions as it fails to clean up.
>
> What happens (or rather, will happen) on a regular/non-mirrored btrfs? Would
> it
> then return an i/o error to the user and/or mark a block as bad? In ZFS, the
> state of the volume changes, noting an issue (also happens on a scrub), and
> the
> user can check this. What I don't like about ZFS is that the user can clear
> the
> condition, and then it appears OK again until another scrub.
>
> -Joe
I think my problem was that the meta data was mirrored but not the actual data.
This lead to total meltdown when data got an error.
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