ZFS re attaching failed device to pool

[Alejandro Imass]

On Tue, Nov 6, 2018 at 8:50 AM Alejandro Imass <aimass at yabarana.com> wrote:

> Dear Beasties,
>
> I have a simple 2 disk pool and one disk started failing and zfs put it in
> a UNAVAIL status. I shut down the server and took it apart, cleaned it and
> removed a third device that was on Sata Port C which I think may have been
> the culprit of the bus fault. This third disk was unrelated to the pool and
> was an older disk which just had some backup data and was running on an old
> enclosure with the SATA wires hanging out, etc. you know, those 5 minute
> hacks that you forget about..
>
> After rebooting, the BIOS saw the failed device and the system booted
> fine. I ran a smartctl long test on the failed device which took like 7
> hours and the report shows no errors and the device is like new.
>
> So now I want to tell ZFS to re-attach the device but the documentation is
> not too clear about this. All the docs, and example I find is physically
> replacing with another device, not the same one.
>
> My question is almost identical to this one which has not been answered
> either:
>
>
> https://forums.freebsd.org/threads/re-attaching-failed-device-to-pool.66027/
>
> So: can I re-attach by running the replace command on the SAME device? I
> haven't tried it, but from the question above it seems that it won't let
> me. Besides I don't want to screw up so if anyone has done this before pls.
> advise how to proceed in these cases.
>
> TIA!
> --
> Alex
>
>
>
I forgot to mention I ran zpool clear zroot and it ran the scrub but did
not put the disk back ONLINE. Here is the result:

root at poseidon:~ # zpool status -v
  pool: zroot
 state: DEGRADED
status: One or more devices could not be used because the label is missing
or
        invalid.  Sufficient replicas exist for the pool to continue
        functioning in a degraded state.
action: Replace the device using 'zpool replace'.
   see: http://illumos.org/msg/ZFS-8000-4J
  scan: scrub repaired 0 in 0h8m with 0 errors on Tue Nov  6 05:27:20 2018
config:

        NAME                               STATE     READ WRITE CKSUM
        zroot                              DEGRADED     0     0     0
          mirror-0                         DEGRADED     0     0     0
            5540674508897617692            UNAVAIL      0     0     0  was
/dev/diskid/DISK-WD-WCC4N6XZY8C2
            diskid/DISK-WD-WCC4N2YTRX40p3  ONLINE       0     0     0

errors: No known data errors

Again, TIA for any pointers on how to re-attach the failed disk.

-- 
Alex