A reliable way to change the zpool guid and vdev uuid?

[Matthew Ahrens]

Have you tried "zpool reguid"?

(Wow, I am really behind on this mailing list.)

--matt

On Mon, Nov 10, 2014 at 10:48 PM, Jyoti Sharma <jyoti.mickey at gmail.com>
wrote:

> We support ZFS filesystems ( Zpools really ) with our IntelliSnap hardware
> snapshot technology.
>
>
>
> As part of this we need to read and often modify the zpool guid and vdev
> uuids of the disks involved. Recently we've seen that as our operations
> that change the zpool guid and vdev uuid no longer work for zpools which
> are @ the latest version of the on disk format. As a result of this our
> import operations on the pools fail.
>
>
>
> The sequence of operations we perform are as follows :
>
>
>
> 1.       Take a hardware snapshot of ZFS disks.
>
> 2.       Expose the snapshot LUNs to a different / same box.
>
> 3.       Read and manipulate on-disk ids of the snapshot luns to be unique.
>
> 4.       Rename the pool by writing to on-disk structures.
>
> 5.       Import the pool on the host with a new name.
>
>
>
> With the more recent version of ZPools we see that operation 5 fails. If we
> simply use the zpool import command without running steps 3,4 step 5 works.
> But this is not desirable because as part of our backup operations, at any
> given time we can import :
>
> a.       copy of the source pool to the same host
>
> ----OR------
>
> b.      multiple copies of the source pool on the same host at a time.
>
>
>
> We've used knowledge gained from zfs ondisk specs available online for our
> implementation and these ideas have worked for us  until now. In short we
> suspect a disk format change in the latest or the recent versions of zfs
> that affect the on-disk placement of those ids. We are looking for a
> documented or supported way to change the ids reliably w/o relying on
> on-disk format information in order to keep our codebase future compliant.
>
>
>
>  Thank you.
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