Help needed! ZFS I/O error recovery?

Pawel Jakub Dawidek pjd at
Sun Oct 4 21:36:13 UTC 2009

On Sun, Oct 04, 2009 at 04:22:30PM -0500, Aaron Hurt wrote:
> schroeder# zdb -ll /dev/ad4s1
>    txg=478240
> schroeder# zdb -ll /dev/ad6s1
>    txg=478204
> schroeder# zdb -ll /dev/ad8s1
>    txg=478240
> schroeder# zdb -ll /dev/ad10s1
>    txg=478240

As you can see one of your vdevs (ad6s1) has lower transaction group
number than the others. The difference is quite big (36 uberblocks), so
we may not be able to go that far in the past. It might be that ZFS
doesn't want to use ad6s1, because it is not up-to-date and there are
some errors on one of the other slices.

If you have you data backed up you may try this patch:

Once you run ZFS with the patch you can try setting sysctl
vfs.zfs.maxtxg to 478204 and try importing your pool. It will try to
import the pool on txg from ad6s1. It won't work if the other slices
don't have this uberlock anymore or some earlier data is already
overwritten. Do it on your own risk, as it might mess up your data even

Pawel Jakub Dawidek             
pjd at                 
FreeBSD committer                         Am I Evil? Yes, I Am!
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