Standard RAID Levels

  • RAID 0 - Also known as disk striping. With RAID 0, data is written (striped) in sequential sectors across multiple (more than two) drives. RAID 0 offers essentially no protection for data because there is no redundancy of the data, but can increase performance dramatically as information can be written or retrieved by several drives at once, minimizing the overall
    seek time of larger files.
  • RAID 1 - Also known as drive mirroring. With RAID 1, identical drives are "mirrored" so that as data is written to one drive, the controller copies identical data to a second drive. Mirroring delivers excellent data protection, but carries a high price: because each drive is duplicated for redundancy, half of your total drive capacity is lost. However, there is little
    or no overhead in retrieving data off of a mirrored cache drive when the main drive is also accessible, so RAID 1 delivers good performance in a degraded drive scenario.
  • RAID 4 - Data is striped at a block level across several drives, with parity stored on one drive. The parity information allows recovery from the failure of a single drive. The performance of RAID 4 is very good for reads. Writes, however, require that parity data be upgraded each time. This slows down random writes in particular, though large writes or sequential writes
    are fairly fast.
  • RAID 5 - Employs data striping and parity across all drives in the array creating better performance and security. Since parity information is striped across all drives, lost data can be retrieved and rebuilt from the parity.
  • RAID 6 - extends RAID 5 by adding an additional parity block; thus it uses block-level striping with two parity blocks distributed across all member disks.
  • RAID 10 - A combination of RAID 0 and RAID 1, data is distributed across multiple drives without parity, and then the entire array is mirrored. Although this delivers good performance, the drive storage overhead is 50% because you are mirroring the data.