User's Manual

Virtual Disks 211

Virtual Disks

In order to implement RAID functions, RAID controllers must create a

virtual disk. A virtual disk refers to storage created by a RAID controller from

one or more physical disks. Although a virtual disk may be created from

several physical disks, it is seen by the operating system as a single disk.

Depending on the RAID level used, the virtual disk may retain redundant

data in case of a disk failure or have particular performance attributes. For

more information, see Understanding RAID Concepts.

NOTE: Virtual disks can only be created on a RAID controller.

Considerations Before Creating Virtual Disks

Different controllers have particular characteristics in the way they

implement virtual disks. These characteristics may include use of disk space,

limitations on the number of virtual disks per controller, and so on. It can be

helpful to understand these characteristics before creating virtual disks on the

controller.

The following sections describe controller information that applies to virtual

disks:

• Virtual Disk Considerations for Controllers

• Virtual Disk Considerations for CERC SATA1.5/6ch, and CERC

SATA1.5/2s Controllers

• Problems Associated With Using the Same Physical Disks for Both

Redundant and Non-Redundant Virtual Disks

• Virtual Disk Considerations on Linux

• Number of Physical Disks per Virtual Disk

• Maximum Number of Virtual Disks per Controller

• Calculation for Maximum Virtual Disk Size and the Create Virtual Disk

Express Wizard

You may also want to review the following sections:

• RAID Controller Read, Write, Cache, and Disk Cache Policy