VM's do not actually add that much overhead (depending on the workload - GPU's are notoroiously hard to share). And what most people do not realize is that something like VMware or another hypervisor is also very good at managing things like RAM across many VM's. In many cases you can overprovision (meaning you can have VM's that are technically "assigned" a total amount of RAM or CPU that is more than you even have physically) and still have great performance. The key is always to install the hypervisor on bare metal (dont run VMware on top of Windows or try to host a server where the "base" os is OSX or something).
