I don't have any Pool devices for cache. I just have 4 hard drives with 1 drive for parity. Thats a total of only 5 drives. As a last resort, I unassigned all the drives and then assigned them to the original slots but when I tried to start the array, the web interface just freezes. I was frightened that I would lose my data and so I just downgraded back to version 6. I hope there will be a better update soon.