Apple Xserve RAID - Manual (Page 80)

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Glossary
Common RAID Terms
Array: A grouping of disk drives; also known as a set. Any number of drives can be
configured together to form a RAID array. The same RAID level is applied to all drives in an
array.
Hot spare: A feature of the RAID controller that detects a drive failure and automatically
uses an available drive to rebuild the data from the failed drive. (Not all RAID sets include a
hot spare.)
Mirroring:
A storage method in which the same data is stored twice on two or more
different drives. The data is stored on a primary disk or partition, then “mirrored” to other
disks or partitions.
Parity: A method of storing information that allows all data to be rebuilt if a drive fails.
Parity is more efficient than mirroring because it does not involve duplication of data.
Partitioning:
The division of a disk into smaller segments. The segments appear as
individual disk drives to the host, while maintaining the RAID properties of the set.
RAID set: A specific number of drives grouped together with a single characteristic (for
example, RAID 0, RAID 5). A RAID set can encompass all drive modules on a controller or be
a subset of the total. There can be up to three RAID sets on a controller. A RAID set appears
to a host system as an individual disk drive.
Striping:
The breaking up of data so that it can be stored across multiple disk drives. For
example, if you divide an 80 KB file into five 16 KB pieces, each piece is a stripe.