XigmaNAS

It appears I have two drives with issues, which should I address first? Should both be replaced? One says removed, but I didn't, so maybe I should attempt to online it somehow? Would that be my first task?

I am probably more comfortable with CLI than the GUI.

Sorry for the noob issue.

pool: Tank
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 5h26m with 0 errors on Wed Apr 15 12:54:00 2015
config:

NAME STATE READ WRITE CKSUM
Tank DEGRADED 0 0 0
raidz2-0 DEGRADED 0 0 0
7670713585188487379 UNAVAIL 5 12 0 was /dev/ada2.nop
ada3 ONLINE 0 0 0
ada4 ONLINE 0 0 0
15239251494199840126 REMOVED 0 0 0 was /dev/ada5
ada6 ONLINE 0 0 0

first post the smart values of all your drives.

onlining the drive will not help you here since the pool came up without the drive, the offlined drive will be out of sync and cant wont be part of that pool anymore.

on how to replace drives see here.
http://wiki.nas4free.org/doku.php?id=faq:0149

be careful though you have lost all redundancies.

REMOVED is an unusual condition - either the drive is dead-dead, or possibly there is a problem with connections. Have a look at SMARt, and power down reseat the drive, the sata connectors and the power connectors and see if /dev/ada5 comes good.

Yeap, unless it is a connection issue, removed usually means the drive is dead
Last time I had a drive stated as removed, it wasn't even recognized as a device anymore in several different pcs that I tried - we're talking about totally dead...

Maybe I should rephrase - dead-dead is unusual without prior warning (SMART or operational)

Though not as unusual as we'd like!