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Wednesday, 18 June 2014

Can we keep RDM mapping files in NFS Datastore?

Can we keep RDM mapping files in NFS datastore? This question has been asked to me many times  in my sessions so the answer is NO 

The VMkernel routes physical mode SCSI commands directly over the RDM mapping without any modifications. The RDM vmdk pointer file must reside on a VMFS location, therefore the operation fails because the NFS protocol does not support SCSI commands over this interface. 
When adding an RDM to a virtual machine hosted on an NFS datastore, the Store with Virtual Machine option is grayed out in the Add Raw Device Mapping wizard. Select a specific VMFS Datastore from the available list for the location of the pointer file instead. More Info is available in this
KB article. Let me demonstrate this here:-

1. This is to verify that VM datastore is NFS or not:-

2. First I tried to add the RDM by selecting this option keep the RDM mapping files in the same datastore as the others files are then this action is not allowed:-

3. Then finally I changed the datastore for RDM files to VMFS and other VM files are still in NFS and this action is now allowed:-