ZFS state DEGRADED

[Ico747]

After power cut I have Critical message:

CRITICAL: The volume volume_A (ZFS) state is DEGRADED: One or more devices could not be opened. Sufficient replicas exist for the pool to continue functioning in a degraded state.

What I shall I do to repair?
Add. info
[root@nas] ~# zpool status -x
pool: volume_A
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 9h32m with 0 errors on Sun May 31 12:32:28 2015
config:

NAME STATE READ WRITE CKSUM
volume_A DEGRADED 0 0 0
mirror-0 DEGRADED 0 0 0
14837486859609382136 UNAVAIL 0 0 0 was /dev/gptid/6bdd4c5c-147a-11e1-9175-f46d046472ed
gptid/6c1d329e-147a-11e1-9175-f46d046472ed ONLINE 0 0 0

After restart
CRITICAL: The volume volume_A (ZFS) state is ONLINE: One or more devices has experienced an unrecoverable error. An attempt was made to correct the error. Applications are unaffected.

 

[hugovsky]

System specs?

 

[Ico747]

After restart:
CRITICAL: The volume volume_A (ZFS) state is ONLINE: One or more devices has experienced an unrecoverable error. An attempt was made to correct the error. Applications are unaffected.

Problem solved!
zpool clear volume_A

 

[hugovsky]

Nope.

 

[Robert Trevellyan]

Rebooting has merely cleared the error, it hasn't solved the underlying problem.

What I shall I do to repair?

Run a scrub and some SMART tests, and depending on what they reveal, follow the instructions in the documentation for replacing a failed drive.

After you've solved the underlying problem, set up a proper SMART testing schedule and email notifications.

 

[Darren Myers]

Still need system specs such as motherboard CPU RAM what type of hard drives