Parity
Parity generates a set of redundancy data from two or more parent data sets. The redundancy data can be used to reconstruct one of the parent data sets. Parity data does not fully duplicate the parent data sets. In RAID, this method is applied to entire drives or stripes across all disk drives in an array. A dedicated parity scheme during normal read/write operations is shown below. The types of parity are:
Type | Description |
Dedicated Parity | The parity of the data on two or more disk drives is |
| stored on an additional disk. |
Distributed | The parity data is distributed across all drives in the |
Parity | system. |
If a single disk drive fails, it can be rebuilt from the parity and the data on the remaining drives.
RAID level 3 combines dedicated parity with disk striping. The parity disk in RAID 3 is the last physical drive in a RAID set.
RAID level 5 combines distributed parity with disk striping. Parity provides redundancy for one drive failure without duplicating the contents of entire disk drives, but parity generation can slow the write process.
10MegaRAID Enterprise 1600 Hardware Guide