It's possible, but not through the web GUI; you'd need to use the command line. First you'd need to detach the pool from the web GUI, and of course DO NOT check the box to mark disks as new. Then log into the shell and do this:
Code:
[root@freenas] ~# zpool import
pool: tank
id: 393516748554493526
state: ONLINE
action: The pool can be imported using its name or numeric identifier.
config:
tank ONLINE
mirror-0 ONLINE
gptid/8c9228b1-6e74-11e4-808f-08002762ec9a ONLINE
gptid/0bced4c9-6e75-11e4-b33f-08002762ec9a ONLINE
[root@freenas] ~# zpool import tank
cannot mount '/tank': failed to create mountpoint
cannot mount '/tank/.system': failed to create mountpoint
cannot mount '/tank/.system/cores': failed to create mountpoint
cannot mount '/tank/.system/rrd-93bc65e2ee7f41d0a1fe412de34ba473': failed to create mountpoint
cannot mount '/tank/.system/samba4': failed to create mountpoint
cannot mount '/tank/.system/syslog-93bc65e2ee7f41d0a1fe412de34ba473': failed to create mountpoint
[root@freenas] ~# zpool status
pool: tank
state: ONLINE
scan: resilvered 1.64M in 0h0m with 0 errors on Mon Nov 17 08:16:11 2014
config:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
gptid/8c9228b1-6e74-11e4-808f-08002762ec9a ONLINE 0 0 0
gptid/0bced4c9-6e75-11e4-b33f-08002762ec9a ONLINE 0 0 0
errors: No known data errors
[root@freenas] ~# zpool detach tank gptid/8c9228b1-6e74-11e4-808f-08002762ec9a
[root@freenas] ~# zpool status
pool: tank
state: ONLINE
scan: resilvered 1.64M in 0h0m with 0 errors on Mon Nov 17 08:16:11 2014
config:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
gptid/0bced4c9-6e75-11e4-b33f-08002762ec9a ONLINE 0 0 0
errors: No known data errors
[root@freenas] ~# zpool export tank
Then use the auto-import feature of the web GUI to re-import the pool.
Caveat: This worked for me, and it's based on Oracle's ZFS docs. However, if you hose your data, it's on you. The "party line" is, if you can't do it from the GUI, don't do it.