174 Configuration: Premium Feature—Virtual Disk Copy• Copying data for improved access—As your storage requirements for avirtual disk change, you can use a virtual disk copy to copy data to a virtualdisk in a disk group that uses drives with larger capacity within the samestorage array. Copying data for larger access capacity enables you to movedata to greater capacity physical disks (for example, 61 GB to 146 GB).• Restoring snapshot virtual disk data to the source virtual disk—The VirtualDisk Copy feature enables you first to restore the data from a snapshotvirtual disk and then to copy the data from the snapshot virtual disk to theoriginal source virtual disk.• Creating a backup copy—The Virtual Disk Copy feature enables you tocreate a backup of a virtual disk by copying data from one virtual disk (thesource virtual disk) to another virtual disk (the target virtual disk) in thesame storage array, minimizing the time that the source virtual disk isunavailable to host write activity. You can then use the target virtual disk asa backup for the source virtual disk, as a resource for system testing, or tocopy 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 DiskMappings feature to recover data from the backup virtual disk you created in theprevious procedure. The Mappings option enables you to unmap the source virtualdisk from its host and then to map the backup virtual disk to the same host.Types of Virtual Disk CopiesYou can perform either offline or online virtual disk copies. To ensure dataintegrity, all I/O to the target virtual disk is suspended during either type ofvirtual disk copy operation. After the virtual disk copy is complete, the targetvirtual disk automatically becomes read-only to the hosts.Offline CopyAn offline copy reads data from the source virtual disk and copies it to a targetvirtual disk, while suspending all updates to the source virtual disk when thecopy is in progress. In an offline virtual disk copy, the relationship is between asource virtual disk and a target virtual disk. Source virtual disks that areparticipating in an offline copy are available for read requests, while thevirtual disk copy displays the In Progress or Pending status. Write requestsare allowed only after the offline copy is complete. If the source virtual disk isformatted with a journaling file system, any attempt to issue a read request to
