RAID 6 protects data with dual parity information distributed
on all member disks.
The data is recoverable from the remaining disks
if one or two disks fail. If a third disk in a
RAID 6 disk array fails, the data is not recoverable.
Recovering a RAID 6 single-disk or dual-disk failure
Whenever one or two disks in a RAID 6 disk array transitions
to the Failed state, the disk array status changes to Degraded. The
disk array remains functional because the data on the failed disk
can be rebuilt using P and Q parity and data on
the remaining disks.