Users Guide

Virtual Disk Considerations On Systems Running 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. For more information, see your operating system
and device documentation.
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.
Related concepts
Virtual Disk Considerations For PERC S100, S110, S130, And S300 Controllers
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.
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.
Virtual Disks
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