I have inherited a FreeNAS 8.3.2 system with a single zpool on it. Unfortunately, it seems to be an odd setup. As far as I can tell, it consists of two vdevs, a raidz2 and a single-drive stripe. Below is the output from zpool status:
pool: Shared
state: ONLINE
scan: resilvered 1.60T in 73h31m with 0 errors on Sun Aug 10 13:19:32 2014
config:
NAME STATE READ WRITE CKSUM
Shared...
Convert a single-disk stripe on a zpool to a mirror stripe
pool: Shared
state: ONLINE
scan: resilvered 1.60T in 73h31m with 0 errors on Sun Aug 10 13:19:32 2014
config:
NAME STATE READ WRITE CKSUM
Shared...
Convert a single-disk stripe on a zpool to a mirror stripe