You can create a virtual disk, use an existing virtual disk, or create Raw Device Mappings (RDMs), which give your virtual disk direct access to SAN. A virtual disk comprises one or more files on the file system that appear as a single hard disk to the guest operating system. These disks are portable among hosts.
You use the Create Virtual Machine wizard to add virtual disks during virtual machine creation. To add disks later, select the Do Not Create Disk option and use the Add Hardware wizard in the Virtual Machine Properties dialog box.
You cannot reassign virtual disks to a different controller type.
You can select from the following options: