User`s guide

CAP Strategy for Selecting a RAID Level

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• Disk capacity utilization (number of disk drives)

• Data redundancy (fault tolerance)

•Disk performance

The controllers make the RAID implementation and the disk drives’ physical

configuration transparent to the host operating system. This transparency means that the

host operating logical drivers and software utilities are unchanged, regardless of the

RAID level selected.

Although a system drive may have only one RAID level, RAID levels can be mixed

within a drive pack (LUN), as illustrated in Figure 4-1.

Figure 4-1 Example of RAID Levels within a Drive Pack (LUN)

In Figure 4-1, the smaller system drive (B0) is assigned a RAID 5 level of operation, while

the larger system drive (B1) is assigned a RAID 0+1 level of operation.

Remember that different RAID levels exhibit different performance characteristics for a

particular application or environment. The controller affords complete versatility in this

regard by allowing multiple RAID levels to be assigned to a drive pack.

Drives are fault-tolerant when you use a RAID level providing redundancy. In the

simplex configuration, however, if the controller or host bus adapter fails, the data is not

accessible until the failure is corrected.

CAP Strategy for Selecting a RAID Level

Capacity, availability, and performance are three benefits, collectively known as CAP,

that should characterize your expectations of the disk array subsystem.

Drive pack B (four disk drives)

RAID 5

RAID 0+1