Glossary, Continued

Consistency Check An examination of the disk system to determine whether all conditions are valid for the specified configuration (such as parity.)

Cold Swap A cold swap requires that you turn the power off before replacing a defective hard drive in a disk subsystem.

Data Transfer Capacity The amount of data per unit time moved through a channel. For disk I/O, bandwidth is expressed in megabytes per second (MB/s).

Degraded A drive that has become non-functional or has decreased in performance.

Disk A non-volatile, randomly addressable, rewritable mass storage device, including both rotating magnetic and optical disks and solid-state disks, or non-volatile electronic storage elements. It does not include specialized devices such as write-once-read-many (WORM) optical disks, nor does it include so-called RAM disks implemented using software to control a dedicated portion of a host computer volatile random access memory.

Disk Array A collection of disks from one or more disk subsystems combined with array management software. It controls the disks and presents them to the array operating environment as one or more virtual disks.

Disk Duplexing A variation on disk mirroring where a second disk adapter or host adapter and redundant disk drives are present.

Disk Mirroring Writing duplicate data to more than one (usually two) hard disks to protect against data loss in the event of device failure. It is a common feature of RAID systems.

Disk Spanning Disk spanning allows multiple disk drives to function like one big drive. Spanning overcomes lack of disk space and simplifies storage management by combining existing resources or adding relatively inexpensive resources. For example, four 400 MB disk drives can be combined to appear to the operating system as one single 1600 MB drive. See also Array Spanning and Spanning.

Cont’d

122MegaRAID Express 500 Hardware Guide