Virtual Machines' Raw Disks cannot be Upgraded to RDMs by the Upgrade Script
Details
When I upgraded to ESX Server 3.0, virtual machines configured
with the raw disk access were not converted to virtual machines
configured with the raw device mapping (RDM) access. How do I convert
these virtual machines to use RDM access?
Solution
If you are using raw disks, you must convert them to RDMs in ESX
Server 2.5 before upgrading virtual machines to ESX Server 3.0.
However, if you have already upgraded your virtual machines to ESX
Server 3.0, do the following:
Migrate the virtual machine that uses the raw disk back to
ESX Server 2.5.
Convert the virtual machine so it can use the RDM.