Users Guide

Parameter Description

performance, and capacity should be considered when selecting the RAID

level. For more information, see the topic Summary Of RAID Levels.

Stripe Element Size Stripe Element Size specifies the size of the segments written to each physical

disk in a RAID 0, 1, 5, 6, 10, 50, and 60 virtual disk. You can set the stripe

element size to 64 KB 128 KB, 256 KB, 512 KB, or 1024 KB. The default and

recommended stripe element size is 64 KB.

A larger stripe element size provides better read performance if your system

mostly does sequential reads.

Write Policy Write Policy specifies the controller write policy. You can set the write policy

to Write-Back or Write-Through.

In Write-Back caching, the controller sends a data transfer completion signal

to the host when the controller cache has received all the data in a

transaction.

NOTE: If a Battery Backup Unit (BBU) is present, the default cache setting

is Write-Back. If no BBU is present, the default cache policy default

setting is Write-Through.

NOTE: If Write-Back is enabled and the system is quickly turned off and

then on, the controller may pause as the system flushes cache memory.

Controllers that contain a battery backup default to Write-Back caching.

In Write-Through caching, the controller sends a data transfer

completion signal to the host when the disk subsystem has received all

the data in a transaction.

Read Policy Read-Ahead enables the read ahead feature for the virtual disk. You can set

the parameter to Read-Ahead, No-Read-Ahead, or Adaptive. The default is

Adaptive-Read-Ahead.

Read-Ahead specifies that the controller uses Read-Ahead for the current

virtual disk. Read-Ahead capability allows the controller to read sequentially

ahead of requested data and store the additional data in cache memory,

anticipating that the data is required soon.

No-Read-Ahead specifies that the controller does not use read ahead for the

current virtual disk.

Adaptive specifies that the controller begins using Read-Ahead if the two

most recent disk accesses occurred in sequential sectors. If all read requests

are random, the algorithm reverts to No-Read-Ahead; however, all requests

are still evaluated for possible sequential operation.

Virtual Disk Management

Creating Virtual Disks

NOTE: Combining SAS and SATA disk drives within a virtual disk is not supported. Also, combining

disk drives and SSDs within a virtual disk is not supported.