[zfs-discuss] Upgrading vdev mirror from ashift=9 to ashift=12 : 512B to 4K transition

Gregor Kopka zfs-discuss at kopka.net
Sat Jan 2 02:27:21 EST 2016



Am 01.01.2016 um 20:20 schrieb fermulator via zfs-discuss:
> Now, as the drives in the vdev with ashift=9 fail, we would presumably
> replace them with newer drives, and it's highly likely these drives
> will have 4K sector size.
> But how can we "migrate" the vdev from ashift=9 to ashift=12?
You can't. There is something in the pipeline from illumous which will
enable to remove vdevs (by moving the data on it to other space in the
pool through clever remapping), but it isn't there yet.

Some open issues on github exist about vdev ashift not being what the
normal guy expects, maybe add a comment there so it'll hopefully get
higher priority.

Current available solutions:

1) Destroy the pool and recreate from backup
2) Take the gamble and offline + zpool labelclear the drives you
currently use for redundancy, create a new pool (single drive vdevs)
from them, zfs send/recv from old to new pool, destroy old pool and
attach (!) the drives from it to create new mirrors (and regain
redundancy). Since you're currently running without redundancy (meaning:
you don't really care about your data) on some of the vdevs this might
be the road for you to take.

Happy new year,

Gregor
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