Configuration Strategies

The most important factors in RAID array configuration are: drive capacity, drive availability (fault tolerance), and drive performance. You cannot configure a logical drive that optimizes all three factors, but it is easy to choose a logical drive configuration that maximizes one factor at the expense of the other two factors, although needs are seldom that simple.

Maximize Capacity RAID 0 achieves maximum drive capacity, but does not provide data redundancy. Maximum drive capacity for each RAID level is shown below. OEM level firmware that can span up to 4 logical drives is assumed.

RAID

Description

Drives

Capacity

Level

 

Required

 

0

Striping

1 – 15

(Number of disks) X capacity of

 

without parity

 

smallest disk

 

 

 

 

1

Mirroring

2

(Capacity of smallest disk) X (1)

 

 

 

 

3

Striping with

3 – 15

(Number of disks) X (capacity of

 

fixed parity

 

smallest disk) - (capacity of 1 disk)

 

drive

 

 

5

Striping with

3 – 15

(Number of disks) X (capacity of

 

floating parity

 

smallest disk) - (capacity of 1 disk)

 

drive

 

 

10

Mirroring and

4 – 14 (Must

(Number of disks) X (capacity of

 

Striping

be a multiple

smallest disk) / (2)

 

 

of 2)

 

30

RAID 3 and

6 – 15 (Must

(Number of disks) X (capacity of

 

Striping

be a multiple

smallest disk) – (capacity of 1 disk X

 

 

of arrays)

number of Arrays)

 

 

 

 

50

RAID 5 and

6 – 15 (Must

(Number of disks) X (capacity of

 

Striping

be a multiple

smallest disk) – (capacity of 1 disk X

 

 

of arrays)

number of Arrays)

 

 

 

 

Note: The maximum number of physical drives supported per controller is 15.

Cont’d

Chapter 5 Configuring MegaRAID Express 500

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