An organization is building a new on-premises file server using eight identical 4 TB SAS drives connected to a hardware RAID controller. The storage volume must remain fully operational if any two disks fail at the same time and should provide the highest possible usable capacity from the eight drives. Which RAID level best meets these requirements?
RAID 6 stripes data across all eight drives while writing two independent parity blocks per stripe. Because the dual-parity information is equivalent to the capacity of only two drives, the array can survive the simultaneous failure of any two disks and still present (8 − 2) × 4 TB of usable space. RAID 10 and RAID 0+1 also tolerate two drive failures in some circumstances, but they always dedicate half of the disks to mirroring, leaving just 16 TB usable. RAID 5 maximizes capacity but protects against only a single drive loss, so it does not meet the fault-tolerance requirement. Therefore, RAID 6 is the only option that satisfies both the dual-disk-failure tolerance and highest usable-capacity criteria.