On Aug 13, 2012, at 8:59 PM, Scott wrote:
> On Mon, Aug 13, 2012 at 10:40:45AM -0700, Richard Elling wrote:
>> On Aug 13, 2012, at 2:24 AM, Sa?o Kiselkov wrote:
>>> On 08/13/2012 10:45 AM, Scott wrote:
>>>> Hi Saso,
>>>> thanks for your reply.
>>>> If all disks are the same, is the root pointer the same?
>>>> Also, is there a "signature" or something unique to the root block that I
>>>> search for on the disk? I'm going through the On-disk specification at the
>>> Nope. The checksums are part of the blockpointer, and the root
>>> blockpointer is in the uberblock, which itself resides in the label. By
>>> overwriting the label you've essentially erased all hope of practically
>>> finding the root of the filesystem tree - not even checksumming all
>>> possible block combinations (of which there are quite a few) will help
>>> you here, because you have no checksums to compare them against.
>>> I'd love to be wrong, and I might be (I don't have as intimate a
>>> knowledge of ZFS' on-disk structure as I'd like), but from where I'm
>>> standing, your raidz vdev is essentially lost.
>> The labels are not identical, because each contains the guid for the device.
>> It is possible, though nontrivial, to recreate.
>> That said, I've never seen a failure that just takes out only the ZFS labels.
> You'd have to go out of your way to take out the labels. Which is just what
> I did (imagine: moving drives over to USB external enclosures, then putting
> them onto a HP Raid controller (which overwrites the end of the disk) - which
> also assumed that two disks should be automatically mirrored (if you miss the
> 5 second prompt where you can tell it not to).
ouch. But that shouldn't be enough.
> Then try and recover the labels without really knowing what you're doing (my
> Suffice to say I have no confidence in the labels of two drives. On OI I can
> forcefully import the pool but with any file that lives on multiple disks (ie,
> over a certain size), all I get is an I/O error. Some of datasets also fail
> to mount.
please tell me you imported readonly?
> Thanks everyone for your input.
>> -- richard
>> ZFS Performance and Training
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