RAID 6 is a highly advanced data protection design requiring at least four hard disk drives and implements a dual-parity striping design.
This design virtually eliminates data loss due to hard disk failure, since a RAID 6 array can sustain two drive failures in a single array with no data loss.
Available from Allied Data Systems , RAID 6 requires at least four hard disk drives and is essentially an improvement and extension of RAID 5.
RAID 6 adds a second independent distributed parity scheme, and data and parity are striped on a block level across multiple array members, just like in RAID 5.
A second set of parity is calculated and written across all the drives, which is desirable as larger disk arrays are considered so the array can tolerate multiple drive failures.
When a disk fails in a parity protected disk array, recovering the contents of the failed disk requires successfully reading the contents of all remaining non-failed disk members of the array.
RAID 6 provides an extremely high fault tolerance and can sustain two simultaneous drive failures without downtime or data loss.