ZFS panic under extreme circumstances (2/3 disks corrupted)

Freddie Cash fjwcash at gmail.com
Mon May 25 16:19:27 UTC 2009

On Mon, May 25, 2009 at 9:12 AM, Thomas Backman <serenity at exscape.org> wrote:
> On May 25, 2009, at 05:39 PM, Freddie Cash wrote:
>> On Mon, May 25, 2009 at 2:13 AM, Thomas Backman <serenity at exscape.org>
>> wrote:
>>> On May 24, 2009, at 09:02 PM, Thomas Backman wrote:
>>>> So, I was playing around with RAID-Z and self-healing...
>>> Yet another follow-up to this.
>>> It appears that all traces of errors vanish after a reboot. So, say you
>>> have a dying disk; ZFS repairs the data for you, and you don't notice (unless
>>> you check zpool status). Then you reboot, and there's NO (easy?) way that I
>>> can tell to find out that something is wrong with your hardware!
>> On our storage server that was initially configured using 1 large
>> 24-drive raidz2 vdev (don't do that, by the way), we had 1 drive go
>> south.  "zpool status" was full of errors.  And the error counts
>> survived reboots.  Either that, or the drive was so bad that the error
>> counts started increasing right away after a boot.  After a week of
>> fighting with it to get the new drive to resilver and get added to the
>> vdev, we nuked it and re-created it using 3 raidz2 vdevs each
>> comprised of 8 drives.
>> (Un)fortunately, that was the only failure we've had so far, so can't
>> really confirm/deny the "error counts reset after reboot".
> Was this on FreeBSD?

64-bit FreeBSD 7.1 using ZFS v6.  SATA drives connected to 3Ware RAID
controllers, but configured as "Single Drive" arrays not using
hardware RAID in any way.

> I have another unfortunate thing to note regarding this: after a reboot,
> it's even impossible to tell *which disk* has gone bad, even if the pool is
> "uncleared" but otherwise "healed". It simply says that a device has failed,
> with no clue as to which one, since they're all "ONLINE"!

Even when using -v?  zpool status -v

Freddie Cash
fjwcash at gmail.com

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