You can designate drives as hot spares using the MegaRAID BIOS Configuration Utility, the MegaRAID Manager, or Power Console Plus.

5.3Creating Logical Drives

Logical drives are arrays or spanned arrays that are presented to the operating system. You must create one or more logical drives.

The logical drive capacity can include all or any portion of an array. The logical drive capacity can also be larger than an array by using spanning. The MegaRAID SCSI 320-0 supports up to 40 logical drives.

5.3.1Configuration 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.

5.3.1.1Maximize 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. Table 5.4 describes the RAID levels, including the number of drives required, and the capacity.

Table 5.4

Capacity for RAID Levels

 

 

 

 

 

RAID

 

 

Drives

 

Level

Description

Required

Capacity

 

 

 

 

 

0

Striping

1

– 30

(Number of disks) X capacity of

 

without parity

 

 

smallest disk

 

 

 

 

 

1

Mirroring

2

 

(Capacity of smallest disk) X (1)

 

 

 

 

 

5

Striping with

3

– 30

(Number of disks) X (capacity of

 

floating parity

 

 

smallest disk) - (capacity of 1 disk)

 

drive

 

 

 

 

 

 

 

 

 

Creating Logical Drives

5-9

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