Raid level 5
  Similar to level 4 but parity block distributed round robin on all drives.

  Stripe using sectors, clusters. 

  All disks have the same work load.

  Can be implemented at hardware or software level.

  Supported by both SCSI and SATA.

  Minimum of 3 disks. Disks should be same size.

  Parity not read on read unless CRC for sector bad. 

  Write requires re-reading of old stripe to calculate the difference.

  Recovery complex because of the random distribution of parity. 
    Most modern systems handle this well, so better choice than level 4.

  Most popular single level RAID.
    In practice, because of on-drive caches,  
      Offers reads almost as fast as Raid 0 and reasonable writes.

  3 to 5 discs best configuration.
  
  Multi-user system where high performance not needed.

  Better for systems with fewer write.

  Raid 6 is 5 with an additional parity system.  
    Provides protection while lost drive is being rebuilt.

    Also requires X+2 drives to implement.  
    Cost effective if total number of drives large.
     
    Raid 6 is useful on very large disk arrays where Raid protection exists
      while a failed drive is being rebuilt.