Users Guide

Table Of Contents
Number Of Physical Disks Per Virtual Disk
There are limitations on the number of physical disks that can be included in the virtual disk. These limitations depend on the
controller. When creating a virtual disk, the controllers support some stripes and spans (methods for combining the storage on
physical disks). Since, the number of total stripes and spans is limited, the number of physical disks that can be used is also
limited. The limitations on stripes and spans affect the possibilities for concatenation and RAID levels as follows:
Maximum number of spans affects RAID 10, RAID 50, and RAID 60.
Maximum number of stripes affects RAID 0, RAID 5, RAID 50, RAID 6, and RAID 60.
Number of physical disks in a mirror is always 2. This property affects RAID 1 and RAID 10.
If RAID 50 and RAID 60, you can use a greater number of physical disks than is possible for other RAID levels. RAID 10 on a
SAS controller with firmware version 6.1 can use a maximum of 256 physical disks. However, the number of connectors on the
controller imposes limitations on how many physical disks can be included in a virtual disk when using RAID 10, RAID 50, or RAID
60. This is because only a limited number of physical disks can be physically attached to the controller.
For information about the maximum number of physical disks supported by a virtual disk, see the virtual disk specifications for
the controller in Supported Features.
Number Of Virtual Disks Per Controller
There are limitations on the number of virtual disks that can be created on the controller. For information about the maximum
number of virtual disks supported by a controller, see the virtual disk specifications for the controller in Supported Features.
Calculation For Maximum Virtual Disk Size
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: SATA and SAS.
SATA RAID Controllers
When using a SATA RAID controller, the controller calculates the 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 the 12 physical disks, because the 12 physical disks can be
included in a RAID 5.
NOTE: SATA RAID does not support disks from MX5016s.
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.
NOTE:
Channel redundancy only applies to controllers that have more than one channel and that attach to an external disk
enclosure.
128 Virtual Disks