Dell EMC PowerVault MD 34XX/38XX Series Storage Arrays Administrator's Guide

When you create a virtual disk copy, you create a copy pair that has a source virtual disk and a target virtual disk on the same storage array.

The source virtual disk is the virtual disk that contains the data you want to copy. The source virtual disk accepts the host I/O read activity and stores the data until it is copied to the target virtual disk. The source virtual disk can be a standard or thin virtual disk.

The target virtual disk is a standard or thin virtual disk in a disk group or disk pool and, if the legacy version is enabled, a legacy snapshot base virtual disk.

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 physical disks 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, 61–146 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.
• Copying data from a thin virtual disk to a standard virtual disk residing in the same storage array. However, you cannot copy data in the opposite direction—from a standard virtual disk to a thin 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 Host 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.