Here is a process to upgrade a VMFS 2 partition to a VMFS 3 partition manually. While this is not something that I am planning on doing myself, the information is now available for all. If you are interested then read on.

The first thing that you will need to do to perform the upgrade is log into the ESX 3 host as root. Once logged in then you need to unload the ESX 3 VMFS drivers that are currently loaded. The unloading of the VMFS drivers is for both VMFS 2 and VMFS 3. To perform this you need to run the commands below. Read the full article at its source here