
Glossary, Continued
Mapping | The conversion between multiple data addressing schemes, especially conversions between |
| member disk block addresses and block addresses of the virtual disks presented to the operating |
| environment by Array Management Software. |
MB | (Megabyte) An abbreviation for 1,000,000 (10 to the sixth power) bytes. It is the same as 1,000 |
| KB (kilobytes). |
Operating Environment The operating environment includes the host computer where the array is attached, any I/O buses and adapters, the host operating system, and any additional software required to operate the array. For
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 | A set of formal rules describing how to transmit data, especially across a network. Low level |
| protocols define the electrical and physical standards to be observed, bit- and byte- ordering, and |
| the transmission and error detection and correction of the bit stream. High level protocols deal with |
| the data formatting, including the message syntax, the |
| sets, and sequencing of messages. |
|
|
| Cont’d |
132MegaRAID Enterprise 1600 Hardware Guide