Hi Folks,
So ZFS says that I have a bad hard drive and that the NAS is running in a degraded state. So for about a month I do nothing until I can afford a replacement hard drive. But before I replace it ZFS is now saying that the drive is good and that it's re-silvering it? I don't get it, can someone explain what happen? 
It does all that I want
Even if this is the case, it is still advisable to update to the stable version. For example, you will get more help in the forum in addition to other reasons.
But before I replace it ZFS is now saying that the drive is good and that it's re-silvering it? I don't get it, can someone explain what happen?
I haven't built a new pool in at least a few years. I've been upgrading my existing pools, so I'm NOT sure of the following.
There's a ZFS feature called "autoreplace". In times past that feature was not ON by default, but I'm not sure what the defaults are when creating a new pool in more recent years.
When ZFS kicks a drive out of a pool (I've personally seen "too many errors"), I'm guessing that it "flags" the drive as bad. With autoreplace=ON, ZFS looks for a new drive, in the same physical slot, to do the "autoreplace". The idea is, physically remove the drive, replace it in the same slot, and boot up. Then ZFS auto resilvers the new drive and adds it to the pool. (With autoreplace turned ON, I've actually done this once.)
Realizing that nothing is perfect:
In your case, if the drive was still installed for several days, weeks or more, ZFS might have lost the "bad drive" marker (maybe it timed out?) and mistook the old drive for a replacement. If that was the case, it would resilver the drive and add it to the pool.
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With the above considered, and also noting that it's possible for ZFS to detect drive issues before SMART does, there's usually a valid reason why ZFS kicks a drive out of the pool. If it happened once, there's a good chance ZFS will kick the same drive out of the pool again. So, if I was in your place, I'd hold onto the drive you ordered.
Save the old drive. I used one of mine for utility purposes, for Dockers, KVM VM's, client E-mail backup, etc. Essentially we're talking about things that I didn't want or need to have in my ZFS pool.
(I do kept an eye on the old drive by regularly tracking it's SMART stat's.)
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