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
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