I'd like to do some testing with virtual hosts. It would be much easier to do it in virtual environment. Few years ago it was impossible (tested with VMWare and VirtualBox). Now, when the VT-X is available and both programs use it, did the picture change?
The answer is: it depends. As far as I can tell, as long, as the virtualization doesn't use hardware virtualization, it is possible. Specifically, it is reported that one can nest virtual box virtualizations here: Virtualization inside a virtualizer, discussions on forums.virtualbox.org