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?
> > 
> > No.
> > 
> >> Also, is there a "signature" or something unique to the root block that I 
> >> can
> >> search for on the disk?  I'm going through the On-disk specification at the
> >> moment.
> > 
> > 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).

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.

Thanks everyone for your input.

>  -- richard
> --
> ZFS Performance and Training
> richard.ell...@richardelling.com
> +1-760-896-4422
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