RAID level 4, block-interleaved parity organization, uses block-level striping,
like RAID 0, and in addition keeps a parity block on a separate disk for
corresponding blocks from N other disks. This scheme is shown pictorially
in Figure 10.3e. If one of the disks fails, the parity block can be used with the
corresponding blocks from the other disks to restore the blocks of the failed
disk.