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 320-1 uses the parity drive 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 15

 

 

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

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