I had exactly the same issue. I have configure 1 drive (Samsung 1TB 7200rpm) as Volume_1. I managed to copy 800 Gb data to it, than after a reboot drive simply dissabeared, and under RAID configuration I could see again "Set RAID type and format"
It means drive and file system were cleared. I could not read the drive with my Win7 PC, but this was not important, because I had a backup. Files system was ext3 anyway
Why this happened? How can I count on this device in the future. This is not a case when disk fails, disk is fine. I have put it back to my PC, and it is working fine.
I can configure raid with 2 disks, but what if volume dissapear again? RAID is a solution if disk fails, but if file system....
This was the reason that I updated to 2.02. Now I have cross site action detected error...
Totally f...ed up!