Aneesh,
VMware ESX server does not support Fibre Channel-attached tape drives, so you might not be able to map an FC-tape to a Virtual Machine (VM).
As of today, the NPIV feature looks like VMware is, ahem, 'experimenting'. Before you can use NPIV, you have to map the disks to the VMkernel, set up RDMs and present to the desired VM. Only then you can add NPIV-enabled WWNs to the VM. Next you grab those WWNs from the .vmx and set up the zoning in the Fibre Channel switches and the LUN masking (=Selective Storage Presentation) on the storage array.
Now you can start the VM and if everything else is set up correctly, NPIV will activate. The VMware documentation has some details on which logfiles to check whether NPIV comes up. If not, nothing horrible happens - the VM has still access to the data - it uses the RDMs!!
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