I have a 6 disk RZ2 pool with an additional disk set up as a spare. This is currently in a degraded status and reporting one disk as unavailable. In my mind I could click on “Replace” and select the spare, however the spare disk does not show up as an available replacement. Can someone confirm for me how the spare disk works and what action I should take?
With the caveat that I don’t use spares.
I would have thought that sde should have appeared under sdl to indicate that the spare has taken over. It doesn’t seem to have done so
I would remove the spare vdev (if you can) and then replace the unavailable disk. Note however that the disk says unavailable, not faulted - which might be a clue
Yes, this is odd.
However, there is a slim chance that the spare is slightly smaller than the minimum size for the RAID-Z2 vDev. That will mean that the spare “sde” would not be capable of replacing the failing device. You can check with;
lsblk -b
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Hot spares will temp replace the degraded disk until the degraded disk can be replaced where the hot spare will return to being a hot spare. The hot spare being unavailable means it acting as a temp replacement until the degraded disk is replace or the hot spare promoted.
Here’s another post on a similar topic - Which of my understandings are wrong: How spares work, or what my box is telling me now? - #9 by DjP-iX
And the how to on promoting a hot spare
on my system, the hot spare is showing as “online” not “unavailable”, so it doesn’t seem to me that it is being used.
Yes, it does seem odd. All the remaining 2TB disks do seem to be the same exact size.
The easiest thing to do, is to remove the Hot Spare, and that will free it up for use as a manual disk replacement.
At some later date, you can add a new Hot Spare. (Though we don’t know if it will take over automatically like it should, since we have not figured out why it did not…)