HP XP48 Manuel du propriétaire télécharger pdf (Page 99)

RAID Technology

Using RAID5

RAID5, like RAID3, processes data between two or more disk drives

simultaneously. RAID5 also saves parity information to a separate disk

drive.

RAID5, unlike RAID3, saves information as blocks of data, which allows

the RAID controller to access each disk for only one stripe of data. This

also allows RAID5 to perform input/output operations on other disks in

parallel. By saving the data as small blocks, this approach permits increased

I/O performance. This makes RAID5 ideal for transaction processing.

In large-scale (sequential) input/output operations, RAID5 permits parallel

processing of the parity blocks, which increases the data transfer rate.

In small-scale input/output operations though, RAID5 must perform extra

read operations from the data and parity disks. This slows the transfer rate

and is called write penalty. To limit this problem, RAID5 distributes the

parity data on several disks in the parity group.

Figure 15. RAID5 Disk Array

Data (block)

B CA

Parity

Generator

Circuit

RAID Controller

G-I

A-C

ABCD

J-L

D-E

1 2 ... 94 95 96 97 98 99 100 101 102 103 104 ... 123 124

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HP XP48 Manuel du propriétaire Page 99