Switch -VD - erase disk contents before creating volume
All files and folders on the target disk will be erased before starting archiving operation, when '-vd' is used. If you create volumes, erasing will be performed before the creation of each volume, giving you the chance to archive to non-empty removable disks. You must be sure that disks do not contain any useful information.
The switch applies only to removable media, the hard disk cannot be erased using it.