NStor Technologies Disk Array Enclosure User Manual download pdf (Page 79)

Glossary

Partition An array virtual disk made up of logical disks rather than

physical ones. Also called logical volume.

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.

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.

AM 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.

Rotated XOR

Redundancy

This term (also known as “parity”) refers to a method of

providing complete data redundancy while requiring only

a fraction of the storage capacity for redundancy. In a

system conﬁgured under RAID 3 and 5, all data and

parity blocks are divided between the drives in such a way

that if any single drive is removed (or fails), the data on it

can be reconstructed using the data on the remaining

drives. (XOR refers to the Boolean “Exclusive-OR”

operator.)

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NStor Technologies Disk Array Enclosure User Manual Page 79

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