Finding Disk ID on a Raw Device Mapping in ESX
vmkfstools is your friend. In ESX 2.5.x you can use the switch “-P” on the “mapping”-file to show you details of the RDM.
# vmkfstools -P /vmfs/FileSystem1/somemachinesdiskfile-META.vmdkin VI3 the switch has changed to “–queryrdm” or just “-q” for short.
# vmkfstools -q /vmfs/FileSystem1/somemachinesdiskfile.vmdk