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APPENDIX
RAID 6
RAID 6 provides the highest reliability. It is similar to RAID 5, but
it performs two different parity computations or the same compu-
tation on overlapping subsets of the data. RAID 6 can offer fault
tolerance greater than RAID 1 or RAID 5 but only consumes the
capacity of 2 disk drives for distributed parity data. RAID 6 is an
extension of RAID 5 but uses a second, independent distributed
parity scheme. Data is striped on a block level across a set of
drives, and then a second set of parity is calculated and written
across all of the drives.
RAID x0
RAID level-x0 refers to RAID level 00, 100, 30, 50 and 60. RAID
x0 is a combination multiple RAID x volume sets with RAID 0
(striping). Striping helps to increase capacity and performance
without adding disks to each RAID x array. The operating system
uses the spanned volume in the same way as a regular volume.
Up to one drive in each sub-volume (RAID 3 or 5) may fail with-
out loss of data. Up to two drives in each sub-volume (RAID 6)
may fail without loss of data. RAID level x0 allows more physi-
cal drives in an array. The benefits of doing so are larger volume
sets, increased performance, and increased reliability.
The following illustration is an example of a RAID level x0 logical
drive.
