RDM High-Level Cover VMware vSphere RDM or Raw Device Mapping is the method to remove levels of abstraction from the storage presented to vSphere VMs. RDMs are used to meet use cases and could be considered a deviation from the ‘normal’;. When creating an RDM, there are two options; Virtual and Physical. A Virtual RDM provides some level of storage abstraction. Physical does not, the full capabilities are visible by the VM.