Yes this is hard to face without backups or some type of replication with the DSS V6 using the iSCSI Auto Failover feature for such cases and though RAID 6 may feel the way to be protected it still is a single point of failure. You might have some chance with a program called GetBack Data that some have found useful but is hard to tell as every data type corruption is different or some type of recovery service like Ontrack.