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Creating Logical Drives 5-9
Copyright © 2002 by LSI Logic Corporation. All rights reserved.
You can designate drives as hot spares using the MegaRAID BIOS
Configuration Utility, the MegaRAID Manager, or Power Console Plus.
5.3 Creating 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.
5.3.1 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.
5.3.1.1 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. Table 5.4 describes the RAID levels, including the number of
drives required, and the capacity.
Table 5.4 Capacity for RAID Levels
RAID
Level Description
Drives
Required Capacity
0Striping
without parity
1 – 30 (Number of disks) X capacity of
smallest disk
1 Mirroring 2 (Capacity of smallest disk) X (1)
5 Striping with
floating parity
drive
3 – 30 (Number of disks) X (capacity of
smallest disk) - (capacity of 1 disk)