MSA2000fc Disk unreadable

[J_Cube]

Hy there
Last week we had the ollowing desaster: MSA2000fc with redundant Controllers. One VDisk and an associated Snappool assigned to each controller. One controller crashed. With the Web Interface of the second controller we restarted the first one, which seemed to function fine and showed all green afterwards. The Volumes assigned to the first controller appeared at the hosts (all Win2003 Server)as unknown and unreadable. The Volumes of the second controller worked fine with their Server. We restarted the hosts, same result. We moved the ownership from Controller A to B, same result. We rebooted both controllers, same result. We repowered the whole system, same result. We rebooted the whole infrastructure (MSA, fc-switches, hosts), same result. I did a verify on the vdisks, MSA said all fine. We called HP 24/7 support and a technician came with a new controller, changed Controller A, same result. At the end of the day we had to delete all Volumes of Contoller A and set them up again. After retreiving the backup everything worked fine. The HP Technician had no idea how this happened, why Controller B did not overtake and why the disks were unreadable.
Does anyone have an idea how we could avoid such an accident in the future and what could have happened?
Regards
Jan