exclusive-or assist make RAID 5 performance exceptional in many different environments.

Uses

Provides high data throughput, especially for large files.

 

Use RAID 5 for transaction processing applications,

 

because each drive can read and write independently. If a

 

drive fails, the MegaRAID SCSI 320-2 uses the distributed

 

parity data to recreate all missing information. Use also for

 

office automation and online customer service that requires

 

fault tolerance. Use for any application that has high read

 

request rates but low write request rates.

 

 

Strong Points

Provides data redundancy and good performance in most

 

environments

 

 

Weak Points

Disk drive performance is reduced if a drive is being rebuilt.

 

Environments with few processes do not perform as well

 

because the RAID overhead is not offset by the

 

performance gains in handling simultaneous processes.

 

 

Drives

3 to 30

 

 

Figure 3.3 shows a RAID 5 array with six disk drives.

Figure 3.3 RAID 5 Array

MegaRAID Controller

Note: Parity is distributed

across drives in the array.

Data Flow

Disk 1

Disk 2

Disk 3

Disk 4

Disk 5

Disk 6

 

 

 

 

 

 

Segment 1

Segment 2

Segment 3

Segment 4

Segment 5

Segment 6

Segment 7

Segment 8

Segment 9

Segment 10

Segment 11

Segment 12

Parity (9–12)

 

Parity (5–8)

 

Parity (1–4)

 

RAID 5

3-5

Copyright © 2002 by LSI Logic Corporation. All rights reserved.