Dell MD3200, MD3220 Types of Virtual Disk Copies

164 Configuration: Premium Feature—Virtual Disk Copy

Reasons to use virtual disk copy include:

• Copying data for improved access—As your storage requirements for a

virtual disk change, you can use a virtual disk copy to copy data to a virtual

disk in a disk group that uses drives with larger capacity within the same

storage array. Copying data for larger access capacity enables you to move

data to greater capacity physical disks (for example, 61 GB to 146 GB).

• Restoring snapshot virtual disk data to the source virtual disk—The Virtual

Disk Copy feature enables you first to restore the data from a snapshot

virtual disk and then to copy the data from the snapshot virtual disk to the

original source virtual disk.

• Creating a backup copy—The Virtual Disk Copy feature enables you to

create a backup of a virtual disk by copying data from one virtual disk (the

source virtual disk) to another virtual disk (the target virtual disk) in the

same storage array, minimizing the time that the source virtual disk is

unavailable to host write activity. You can then use the target virtual disk as

a backup for the source virtual disk, as a resource for system testing, or to

copy data to another device, such as a tape drive or other media.

NOTE: Recovering from a backup copy — You can use the Edit Host-to-Virtual Disk

Mappings feature to recover data from the backup virtual disk you created in the

previous procedure. The Mappings option enables you to unmap the source virtual

disk from its host and then to map the backup virtual disk to the same host.

Types of Virtual Disk Copies

You can perform either offline or online virtual disk copies. To ensure data

integrity, all I/O to the target virtual disk is suspended during either type of

virtual disk copy operation. After the virtual disk copy is complete, the target

virtual disk automatically becomes read-only to the hosts.

An offline copy reads data from the source virtual disk and copies it to a target

virtual disk, while suspending all updates to the source virtual disk when the

copy is in progress. In an offline virtual disk copy, the relationship is between a

source virtual disk and a target virtual disk. Source virtual disks that are

participating in an offline copy are available for read requests, while the

virtual disk copy displays the In Progress or Pending status. Write requests

are allowed only after the offline copy is complete. If the source virtual disk is

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