You could always flip it to RAID 1 (with a hefty performance hit).
The spec doesn't say but realistically it has to be 2 physical drives in a housing. In RAID 0 if either fails you lose everything. In RAID 1 the capacity is halved but if 1 fails you still have all your data (yes....just like a backup....kind of). I don't think either are really appropriate for the needs of photographers.