4 Glossary
Physical Drive
A physical array (or drive) is a collection of physical disks governed by the RAID
management software. A physical drive appears to the host computer as one or more logical
drives.
R
RAID
(Redundant Array of Independent Disks) An approach to using multiple low cost drives as a
group to improve performance, yet also provide a degree of redundancy that makes data
loss remote.
RAID 0
Block “striping” is provided, yielding higher performance than is possible with individual
drives. This level does not provide any redundancy.
RAID 1
Drives are paired and mirrored. All data is 100% duplicated on an equivalent drive.
RAID 10
RAID 10 is a combination of RAID levels 0 and 1. The data is striped across disks as in
RAID 0. Each disk has a mirror disk, as in RAID 1.
RAID 3
Data is striped across several physical drives. For data redundancy one drive is encoded
with rotated XOR redundancy.
RAID 30
Data striping of two or more RAID 3 arrays. RAID level 30 is a combination of 0 and 3.
RAID 5
Data is striped across several physical drives. For data redundancy drives are encoded with
rotated XOR redundancy.
RAID 50
RAID level 50 is a combination of RAID level 0 and 5.
RAID Controller
This refers to the controller card that routes data to and/ or from the CPU. Disk array
controllers perform all RAID algorithms onboard the controller.
Rebuild
The regeneration of all data from a failed disk in a RAID level 1, 3, 5, or 6 array to a
replacement disk. A disk rebuild normally occurs without interruption of application access
to data stored on the array virtual disk.
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