Under RAID 5 parity information is distributed across all the drives. Since there is no
dedicated parity drive, all drives contain data and read operations can be overlapped on
every drive in the array. Write operations will typically access one data drive and one
parity drive. However, because different records store their parity on different drives, write
operations can usually be overlapped.
RAID 6 is similar to RAID 5 in that data protection is achieved by writing parity information
to the physical drives in the array. With RAID 6, however, two sets of parity data are used.
These two sets are different, and each set occupies a capacity equivalent to that of one of
the constituent drives. The main advantage of RAID 6 is High data availability – any two
drives can fail without loss of critical data.
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