Why would I want to do this?
well para virtual scsi controllers do not require as much system resources from the host to run and therefore give you better performance. woohoo how do we do this?
1. While the VM is running, add a new disk with SCSI ID 1:0 (or 2:0 if 1:x already exists)
2. This will also add a new SCSI controller. BEFORE closing the settings dialog change its type to pvscsi.
3. Inside the VM check with Disk Manager if the new disk appears there (you might need to rescan or manually install the pvscsi driver from the VMware Tools)
4. When the disk appears the pvscsi driver has been successfully added and activated.
5. Shutdown the VM and remove the newly added disk (this will also remove the additional SCSI controller).
6. Change the type of the first SCSI controller to pvscsi and power on the VM again.