Dell PowerVault MD3220 Cli Manual page 90

You can select snapshot virtual disks as the source virtual disk for a virtual disk
copy. Selecting a snapshot virtual disk is a good use of this feature, because it
enables complete backups without significant impact to the storage array I/O.
However, some I/O processing resources are lost to the copy operation.
The Snapshot Virtual Disk feature can be used with the Virtual Disk Copy
feature to back up data on the same storage array and to restore the data on the
snapshot virtual disk back to its original source virtual disk.
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Using the Virtual Disk Copy Feature