A Raw Device Mapping (RDM) may be required in special cases where an application or guest operating system requires access to a device directly, or with a native filesystem on the device, unlike the normal methodology of the disk residing on a VMFS backed datastore. To enable this, a LUN can be directly provisioned to a virtual machine through the use of RDMs.
Attaching a Raw Device Mapping to a virtual machine
Getting ready
Present the LUN to all the ESXi hosts in the cluster, this is imperative to ensure virtual machine mobility. In a cluster, it's quite typical for a virtual machine to restart or migrate on other hosts, the LUN can be continuously accessed by the virtual machine.
Needless to state, this is a prerequisite...
