To access virtual disks, a virtual machine uses virtual SCSI controllers. These virtual controllers appear to a virtual machine as different types of controllers, including BusLogic Parallel, LSI Logic Parallel, LSI Logic SAS, and VMware Paravirtual. You can change the SCSI controller type, allocate bus sharing for a virtual machine, add a paravirtualized SCSI controller, and enable or disable VMI paravirtualization.