zfs pool degraded - start over or possibly fix?

[nas-hawk]

I had been running version 9.1 (or maybe 9.2) for quite some time. After a power outage I heard some noise upon restarting the server and decided to upgrade. I figured one or perhaps both disks were having problems. Fortunately I was able to copy all of my data to another disk on my network.

I saved my configuration and decided it would be a good time to remove the drives and rid the case of dust, etc. I'm pretty sure that I reversed some sata cables when I put everything back together.

Did the upgrade to the latest embedded version and imported my config file. Of course I did something wrong. I tried to fix using advice from forum searches but no luck (although I think I successfully scrubbed the bad drive.. Here is my zfs information output:
-------------------------------------------------------------------------------------------------------
pool: themirror
state: DEGRADED
status: One or more devices could not be opened. Sufficient replicas exist for
the pool to continue functioning in a degraded state.
action: Attach the missing device and online it using 'zpool online'.
see: http://illumos.org/msg/ZFS-8000-2Q
scan: scrub repaired 0 in 0h21m with 0 errors on Thu Mar 10 01:34:17 2016
config:

NAME STATE READ WRITE CKSUM
themirror DEGRADED 0 0 0
mirror-0 DEGRADED 0 0 0
16560157284363385833 UNAVAIL 0 0 0 was /dev/ada2
ada2 ONLINE 0 0 0 block size: 512B configured, 4096B native

errors: No known data errors
-------------------------------------------------------------------

If it is fixable should I do it? If not, I am not sure how to delete/destroy the pool and start over. I tried zpool replace with that long string of numbers but got error messages.

Any help is greatly appreciated. BTW I also noticed when watching the boot process that the UNAVAIL drive showed it as a 3 GB/s drive but it is identical to the other one which showed as running at 6 GB/s. Don't know if that's related or not.

[kenZ71]

Possibly a drive is failing, does SMART indicate all drives are healthy?

If yes then try to make sure all cables are fully connected.

An chance you have a backup config file? If you open in a text editor you should be able to determine the drive sequence.

[nas-hawk]

I'll take a look at SMART (never used it before). I do have a backup config. I'll take a look.

Thx

[nas-hawk]

Just wanted to let everyone know that I upgraded and replaced my mirror with 2 bigger drives and recopied ALL of the files back to my nas.

I guess that's the beauty of having the ability of saving your data even when one drive gets corrupted.

Thanks to those who replied. Always appreciate the help.