Can't use gpt labels re-importing pool

Scot Hetzel swhetzel at
Thu Nov 26 10:29:18 UTC 2009

On 11/26/09, Jeremy Chadwick <freebsd at> wrote:
> I'm a bit curious about something, so maybe someone can help me
>  understand:
>  Why are people bothering with GPT labels (or in some cases, glabels)
>  when AHCI (whether it be ataahci.ko or ahci.ko) is in use?  Under what
>  circumstance would the device name change dynamically in this situation?

There was a thread about this problem where the drives had changed
their device names due to a change in the kernel drive  (Current list
from July):

Through out this thread there were various suggests on how he could
recover the system, and prevent the problem from occurring in the

One of the suggestions was that use of zpool replace to change from
device names to using glabel labels.

>  I've never witnessed this happening with AHCI, at least on Intel
>  systems, and I've hot-swapped hard disks many times over.

Using glabels, gpt labels, or gptid solves the problem of not needing
to remember which device name the drive originally had.  For instance,
on a zfs zraid pool with 3 disks (ad1 ad2 ad3) you could disconnect
the pool from one computer and connect it to another system and it
wouldn't matter which order you reconnected the drives (1 2 3 or 3  1
2) as the pool would still be recognized when it is imported on the
new system.  Also if the new system already has drives ad1 and ad2, it
wouldn't matter.


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