Dell PowerVault MD3220 - Manual (Page 164)

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.
Offline Copy
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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