User's Manual

Back to Contents Page
 Virtual Disks
Dell OpenManage Server Administrator Storage Management User's Guide
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.
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:
l Virtual Disk Considerations for PERC 4/SC, 4/DC, 4e/DC, 4/Di, 4e/Si, 4e/Di, PERC 5/E, PERC 5/i, PERC 6/E, and PERC 6/I Controllers
l Virtual Disk Considerations for CERC SATA1.5/6ch, and CERC SATA1.5/2s Controllers
l Problems Associated With Using the Same Physical Disks for Both Redundant and Non-Redundant Virtual Disks
l Virtual Disk Considerations on Linux
l Number of Physical Disks per Virtual Disk
l Maximum Number of Virtual Disks per Controller
l Calculation for Maximum Virtual Disk Size and the Create Virtual Disk Express Wizard
You may also want to review the following sections:
l RAID Controller Read, Write, Cache, and Disk Cache Policy
l Understanding Hot Spares
l Controller-supported Stripe Sizes
l Rescan to Update Storage Configuration Changes
l Time Delay in Displaying Configuration Changes

Virtual Disk Considerations for PERC 4/SC, 4/DC, 4e/DC, 4/Di, 4e/Si, 4e/Di, PERC 5/E,
PERC 5/i, PERC 6/E, and PERC 6/I Controllers
In addition to the considerations described in this section, you should also be aware of the controller limitations described in Number of Physical Disks per
Virtual Disk.
Be aware that the following considerations apply when creating virtual disks:
l Creating virtual disks on PERC 4/SC, 4/DC, 4e/DC, 4/Di, 4e/Si, 4e/Di, 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.
Considerations Before Creating Virtual Disks
Creating Virtual Disks
Reconfiguring/Migrating Virtual Disks
Starting and Target RAID Levels for Virtual Disk Reconfiguration and
Capacity Expansion
Maintain Integrity of Redundant Virtual Disks
Rebuilding Redundant Information
Virtual Disk Bad Block Management
Virtual Disk Properties and Tasks
Create Virtual Disk Express Wizard (Step 1 of 2)
Create Virtual Disk Express Wizard (Step 2 of 2)
Create Virtual Disk Advanced Wizard (Step 1 of 4)
Create Virtual Disk Advanced Wizard (Step 2 of 4)
Create Virtual Disk Advanced Wizard (Step 3 of 4)
Create Virtual Disk Advanced Wizard (Step 4 of 4)
Span Edit
Virtual Disk Task: Reconfigure (Step 1 of 3)
Virtual Disk Task: Reconfigure (Step 2 of 3)
Virtual Disk Task: Reconfigure (Step 3 of 3)
Format and Initialize; Slow and Fast
Initialize
Virtual Disk Task: Delete
Virtual Disk Task: Rename
Virtual Disk Task: Change Policy
Split Mirror
Unmirror
Assign and Unassign Dedicated Hot Spare
Virtual Disk Task: Replace Member Disk
(Step 1 of 2)
Virtual Disk Task: Replace Member Disk
(Step 2 of 2)
NOTE: Virtual disks can only be created on a RAID controller.
NOTE: In addition to this document, review the hardware documentation that is provided with the controllers. Reviewing the hardware documentation
along with this document may provide a better understanding of the controller limitations.