Glossary, Continued

Format

The process of writing zeros to all data fields in a physical drive (hard drive) to map out

 

unreadable or bad sectors. Because most hard drives are factory formatted, formatting is usually

 

only done if a hard disk generates many media errors.

GB

Shorthand for 1,000,000,000 (10 to the ninth power) bytes. It is the same as 1,000 MB

 

(megabytes).

Host-based Array A disk array with an Array Management Software in its host computer rather than in a disk subsystem.

Host Computer Any computer that disks are directly attached to. Mainframes, servers, workstations, and personal computers can all be considered host computers.

Hot Spare A stand-by drive ready for use if another drive fails. It does not contain any user data. Up to eight disk drives can be assigned as hot spares for an adapter. A hot spare can be dedicated to a single redundant array or it can be part of the global hot-spare pool for all arrays controlled by the adapter.

Hot Swap The substitution of a replacement unit in a disk subsystem for a defective one, where the substitution can be performed while the subsystem is running (performing its normal functions). Hot swaps are manual.

I/O Driver A host computer software component (usually part of the operating system) that controls the operation of peripheral controllers or adapters attached to the host computer. I/O drivers communicate between applications and I/O devices, and in some cases participates in data transfer.

Initialization The process of writing zeros to the data fields of a logical drive and generating the corresponding parity to put the logical drive in a Ready state. Initializing erases previous data and generates parity so that the logical drive will pass a consistency check. Arrays can work without initializing, but they can fail a consistency check because the parity fields have not been generated.

Logical Disk A set of contiguous chunks on a physical disk. Logical disks are used in array implementations as constituents of logical volumes or partitions. Logical disks are normally transparent to the host environment, except when the array containing them is being configured.

Logical Drive A virtual drive within an array that can consist of more than one physical drive. Logical drives divide the contiguous storage space of an array of disk drives or a spanned group of arrays of drives. The storage space in a logical drive is spread across all the physical drives in the array or spanned arrays. Each MegaRAID adapter can be configured with up to 40 logical drives in any combination of sizes. Configure at least one logical drive for each array.

Cont’d

Glossary131