VMWare Fault Tolerance – Potential Bug or Issue in VMWare 5.1

Background / Setup

I've got a fresh install of vCenter Server 5.1 and associated components.

I've taken all steps (as far as I can tell) to enable FT, and it worked the first time (yanked a power cord and watched a VM keep working — an awesome feeling, by the way).

The steps I took were:

• Create an HA cluster with two servers
• Add an additional Virtual VMkernel NIC to handle FT traffic on each host
• Ensured that all hosts have access to multiple network storage devices (EMC and netapp).
• On a VM, changed the CPU/MMU Virtualization option to "Use Intel VT-x/AMD-V For Instruction set virtualization and software for MMU virtualization"
• Right-clicked on the VM and selected "turn On fault tolerance". This completed successfully.

Again, this worked.

Problem

Now, however, in the VM menu, after all hosts have come back on-line the option is again to "turn On Fault tolerance" (I thought once on, it would stay on?)

Additionally, if I click to turn fault tolerance on again, I receive the message "The virtual machine is running in a monitor mode that is incompatible for fault tolerance." However, selecting VT-x/AMD-V is what fixed this problem last time before my initial test that worked, and it is still selected in the menu.

Questions

• Is this a bug in the display, and the machine is still fault tolerant?
• Is this something I need to reconfigure each time?
• Once a machine has been configured for fault tolerance, does it remain in that mode perpetually? My guess would be that it should, but this experience makes me question it.

Update: More information (potential lead?)

To make matters more interesting, I just tried the following:

• Set CPU/MMU on the VM back to "Automatic"
• Rebooted the VM
• Set the CPU/MMU back to the intel setting that worked the first time
• Rebooted the VM
• Clicked "Turn Fault Tolerance on"
• …and received the same error.

Thanks!