RAID 4 – Block-Interleaved Parity With this level, the striping unit is a disk block – a parity block is maintained on a separate disk for corresponding blocks from a number of other disks. 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. A diagrammatic representation of RAID 4 is shown in Figure 19.4(e).