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The Lone Lemon
Mar 22, 2006
...rides again

Posting this in the faint hope that there is a ZFS nerd lurking in this subforum...

Problem description: ZFS set up as striped mirror pool (like RAID 10). One mirror has two disks down. Kaboom. I moved the 4 disks in the pool to a new external housing. On reboot, one of the disks was reported as missing from the pool. It looks like its partition table got corrupted somehow (cosmic rays? static discharge?). The other disk in that mirror was working fine, so I went to bed thinking I'd fix it in the morning by wiping the disk and using the zfs replace command to resilver it from scratch. Guess what? Overnight, disk 2 failed. Spectacularly. SMART data shows thousands of reallocated sectors. So, with both mirrors down, the pool is in a failed state.

Oh yeah, and I'm using the whole disk, so there should be one giant partition, followed by an 8mb partition at the end.

So I'm really hoping there's a relatively easy way (n.b. I don't know how to deal with hextables) to repair the partition table. Or copy it from the other disk in the mirror (I think the partition table on that one is still okay and I'd be willing to risk it). The usual tools like testdisk don't support ZFS partitions, it seems.

Before everyone yells at me: all critical data is backed up. What will be hard to restore is the labyrinth of shares and symlinks. I can do it, but we're talking hours and hours of fiddling with symlinks and permission bits to get everything just right. So I'm hoping one of you knows how to do this (pretty sure ZFS keeps a backup partition table at the end of the drive, but I can't find any references on how to restore it).

Attempted fixes:
- Tried gparted's recovery option (ran it overnight, did nothing, reported nothing to recover when I exited
- Connected the disk bay to my Windows machine to check SMART status. Failed drive was borked (see above), drive with missing partition appears fine.
- Ran Klennet's ZFS Recovery. All files are present with good checksums. If I drop $400, I can copy them off using Klennet. Don't really want to do that.

Recent changes: Only physically moving the disks.


Operating system: Ubuntu 18.04.5 LTS, 64-bit

System specs: Not really relevant, I don't think.

Location: Again, not super relevant.

I have Googled and read the FAQ: Yes, Googled, can't find FAQ. Which FAQ?

If anyone can point me in the right direction, I will be very grateful and name my first born child after you. No, I won't. He's already 7 and I might have trouble convincing him to take a new name like TubeLube69.


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