If hardware memory virtualization is available (this may depend on hardware vendors and BIOS settings), ESX(i) will use it. There is no way to enable or disable it at a global level.
However, you can enable/disable it per VM: Look at -> Advanced Options -> CPU/MMU virtualization.
I would recommend leaving this at the default ("automatic"). ESX will then choose the method that will give best performance with the selected guest OS version.
Andreas
- VMware Front Experience Blog
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