Edit 13/12/12 - At this stage it would appear to be related to Western Digital (and possibly others) Advanced Format 4K block sizes. This link goes some way into describing the issue, however the ...
I have set up a RAW mapped storage device which is shared between 3 VMs. In the guest OSs the disk shows up fine but when I try to set up multipathing I can only see one path. In the virtual machine ...