Glossary, Continued
Parity | Parity is an extra bit added to a byte or word to reveal errors in storage (in RAM or disk) |
| or transmission. Parity is used to generate 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. However, 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. Parity |
| consists of dedicated parity, in which the parity of the data on two or more drives is stored |
| on an additional drive, and distributed parity, in which the parity data are distributed |
| among all the drives in the system. If a single drive fails, it can be rebuilt from the parity |
| of the respective data on the remaining drives. |
Partition | An array virtual disk made up of logical disks rather than physical ones. Also known as |
| logical volume. |
Physical Disk | A hard disk drive that stores data. A hard disk drive consists of one or more rigid magnetic |
| discs rotating about a central axle with associated read/write heads and electronics. |
Physical Disk Roaming The ability of some adapters to detect when hard drives have been moved to a different slots in the computer, for example, after a hot swap.
Protocol
RAID
Cont’d
126MegaRAID Express 500 Hardware Guide