Hope this will help you
Comment by Andre
If you want to convert the RDM to a virtual disk with minimum downtime, you could simply shut down the VM, remove the pRDM from the VM, and re-attach it as a vRDM (using the same SCSI ID), and then power the VM on again. When you remove the pRDM from the VM, choose to delete the pRDM from the disk (this will only delete the mapping file), otherwise the raw LUN will not be available as a vRDM. After this you will be able to use Storage vMotion to migrate the VM. In order for the vRDM to be converted ino a virtual disk, you need to select a target virtual disk format (thick or thin) in the wizard, i.e. don't select "Same as source"!