Use the vmkfstools command to create a Raw Device Mapping (RDM) file on a VMFS volume and map a raw LUN to this file. After this mapping is established, you can access the LUN as you would a normal VMFS virtual disk. The file length of the mapping is the same as the size of the raw LUN it points to.

-r|--createrdm device

When specifying the device parameter, use the following format:

/vmfs/devices/disks/disk_ID:P

Example for Creating a Virtual Compatibility Mode RDM

In this example, you create an RDM file named my_rdm.vmdk and map the disk_ID raw disk to that file.

vmkfstools -r /vmfs/devices/disks/disk_ID my_rdm.vmdk

You can configure a virtual machine to use the my_rdm.vmdk mapping file by adding the following lines to the virtual machine configuration file:

scsi0:0.present = TRUE 
scsi0:0.fileName = /vmfs/volumes/myVMFS/my_rdm.vmdk