User's Manual
Be aware that the following considerations apply when creating virtual disks:
l Creating virtual disks on PERC 5/E, PERC 5/i, PERC 6/E, and PERC 6/I controllers. When you create a virtual disk, you specify which physical disks
are to be included in the virtual disk. The virtual disk you create spans the specified physical disks. Depending on the size of the virtual disk, the virtual
disk may not consume all of the space on the physical disks. Any leftover space on the physical disks cannot be used for a second virtual disk unless the
physical disks are of equal size. In addition, when the physical disks are of equal size and you can use the leftover space for a second virtual disk, this
new virtual disk cannot expand to include any physical disks not included in the original virtual disk.
l Expanding virtual disks. You can only use the Reconfigure task to expand a virtual disk that uses the full capacity of its member physical disks. For
more information, see "Virtual Disk Task: Reconfigure (Step 1 of 3)."
l Reconfiguring virtual disks. The Reconfigure task is not available when you have more than one virtual disk using the same set of physical disks. You
can, however, reconfigure a virtual disk that is the only virtual disk residing on a set of physical disks. See "Virtual Disk Task: Reconfigure (Step 1 of 3)"
for more information.
l Virtual disk names not stored on controller. The names of the virtual disks that you create are not stored on the controller. This means that if you
reboot using a different operating system, the new operating system may rename the virtual disk using its own naming conventions.
l Creating and deleting virtual disks on cluster-enabled controllers. There are particular considerations for creating or deleting a virtual disk from a
cluster-enabled controller.
l Implementing channel redundancy. A virtual disk is channel-redundant when it maintains redundant data on more than one channel. If one of the
channels fails, data will not be lost because redundant data resides on another channel. For more information, see "Channel Redundancy and Thermal
Shutdown."
l Rebuilding data. An failed physical disk that is used by both redundant and nonredundant virtual disks cannot be rebuilt. Rebuilding a failed physical
disk in this situation requires deleting the nonredundant virtual disk.
Virtual Disk Considerations on Linux
On some versions of the Linux operating system, the virtual disk size is limited to 1TB. Before creating a virtual disk that is larger than 1TB, you should make
sure that your operating system supports this virtual disk size. The support provided by your operating system depends on the version of the operating
system and any updates or modifications that you have implemented. In addition, you should investigate the capacity of your peripheral devices to support a
virtual disk that is larger than 1TB. See your operating system and device documentation for more information.
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, controllers support a certain number of stripes and spans (methods for combining the storage on physical disks). Because 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 RAID
levels as follows:
l Maximum number of spans affects RAID 10, RAID 50, and RAID 60.
l Maximum number of stripes affects RAID 0, RAID 5, RAID 50, RAID 6, and RAID 60.
l Number of physical disks in a mirror is always 2. This affects RAID 1 and RAID 10.
In the case of RAID 50 and RAID 60, you can use a greater number of physical disks than is possible for the 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 on how many physical disks a controller supports per virtual disk, see the virtual disk specifications for the controller in "Supported Features."
Maximum Number of Virtual Disks per Controller
Controllers have limitations on how many virtual disks can be created on the controller. For information on how many virtual disks the controller supports, see
the virtual disk specifications for the controller in "Supported Features."
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: SAS."