Existe uma opção que permite importar o pool com um dispositivo quebrado. Foi assim que consegui recuperar a piscina:
# zpool export tank
# zpool import -m tank
# zpool status tank
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: none requested
config:
NAME STATE READ WRITE CKSUM
tank DEGRADED 0 0 0
mirror-0 ONLINE 0 0 0
gpt/disk1 ONLINE 0 0 0
gpt/disk2 ONLINE 0 0 0
logs
6324139563861643487 UNAVAIL 0 0 0 was /dev/md1
cache
gpt/disk3 ONLINE 0 0 0
errors: No known data errors
# zpool clear tank
# zpool remove tank 6324139563861643487
# zpool status tank
pool: tank
state: ONLINE
scan: none requested
config:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
gpt/disk1 ONLINE 0 0 0
gpt/disk2 ONLINE 0 0 0
cache
gpt/disk3 ONLINE 0 0 0
errors: No known data errors