User's Manual

Virtual Disks 217
Calculation for Maximum Virtual Disk Size and the Create Virtual Disk
Express Wizard
The Create Virtual Disk Express Wizard displays the minimum and
maximum values for the virtual disk size. This section describes how the
maximum possible size for the virtual disk is calculated based on the
controller type. To identify the controller type, see RAID Controller
Technology: SCSI, SATA, ATA, and SAS.
SCSI, CERC SATA, and CERC ATA RAID Controllers
When using a SCSI, CERC SATA, or CERC ATA RAID controller, the
controller calculates a maximum virtual disk size based on your RAID level
selection and the available physical disk space provided by all suitable
physical disks attached to the controller. For example, if the controller
contains 12 physical disks with available space and you have specified a RAID
5, then the controller calculates the maximum virtual disk size based on the
disk space provided by all 12 physical disks, because all 12 physical disks can
be included in a RAID 5.
SAS RAID Controllers
When using a SAS controller, the controller calculates the maximum virtual
disk size based on the available disk space provided by the minimum number
of physical disks required to create the RAID level you selected. For example,
if you specified a RAID 5, then the controller calculates the maximum virtual
disk size based on three physical disks, because only three physical disks are
required to create a RAID 5.
Channel Redundant Virtual Disks
When creating a virtual disk, it is possible to use disks attached to different
channels to implement channel redundancy. This configuration might be
used for disks that reside in enclosures subject to thermal shutdown. For
more information, see the following:
• SMART Thermal Shutdown
• Channel Redundancy and Thermal Shutdown
NOTE: Channel redundancy only applies to controllers that have more than one
channel and that attach to an external disk enclosure.