Compaq StorageWorks 4000 - RAID Array Guide de l'utilisateur télécharger pdf (Page 150)

Hard Drive Arrays

If you will be storing non-critical data, and space and performance are both

important, RAID 0 offers the best of both parameters. However, RAID 0 has

no data protection and you will have to rely on backups in case of hardware

failure.

Distributed data guarding, also called RAID 5, stores parity data across all the

drives in the array. Spreading the parity across all the drives allows more

simultaneous read operations and higher performance than data guarding

(RAID 4). If a drive fails, the controller uses the parity data and the data on the

remaining drives to reconstruct data from the failed drive. This allows the

system to continue operating with slightly reduced performance until the failed

drive is replaced.

Distributed data guarding requires an array with a minimum of three physical

drives and allows a maximum of 12 drives. Therefore, in an array containing

three physical drives, distributed data guarding uses only 33 percent of the

total logical drive storage capacity for fault tolerance, while a 12-drive

configuration uses only 7 percent.

DATA

DATADATADATA

P = Parity

WAR2-053.AI, 9-3.EPS

Figure E-5. Distributed data guarding distributes the redundant data [P]

throughout the physical drives

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Compaq StorageWorks 4000 - RAID Array Guide de l'utilisateur Page 150