VirtualBox, VMWare Fusion, and Parallels Desktop are probably your best bets out of the 3 options considered. 'Free and mostly open source' is the primary reason people pick VirtualBox over the competition. This page is powered by a knowledgeable community that helps you make.
I am researching into the Mac Pro as my next PC (purpose is software dev with virtual test labs etc). I am thinking of running ESX on such a box. Is it possible to scrap the OS and deploy just the hypervisor? A colleague in my company says he runs VMWare Fusion on a Mac (not sure if it is the Pro), and then ESX within that, which holds the VMs he can RDP to. How well would this approach work? The immediate thing is that this approach has so many layers so ESX is talking to VMWare Fusion and not the hardware layer directly - am I correct?
What would the ideal approach be? You are not going to want to run ESX from within Fusion. ESX is an X86 based hypervisor that install directly on a server (its like a lightweight OS that can run VMs) and is intended (and priced) for enterprise use. Fusion is a hypervisor that runs from within your OSX install as a process and allows you to install virtual machines 'on top' of OSX. In short, you don't need to look at ESX, Fusion alone would be sufficient.
The other route that I have seen is Parallels desktop, which seems quite popular. You definitely wouldn't want to run Fusion - ESX - VMs. That's a hypervisor inside a hypervisor, which is pointless. As Chris above stated, just using VMware Fusion is sufficient if that is what you want & just create VMs from within Fusion. The only downside to this is you need a fully functional OS to run VMware Fusion, so that adds a lot of overhead and you're losing hardware resources to that. If you are looking for a true hypervisor solution, look in to. With this product, the hypervisor itself is the OS and all you need to get your VMs up and running.
![Hypervisor Hypervisor](/uploads/1/2/5/4/125445888/256461039.png)
![Mac Mac](/uploads/1/2/5/4/125445888/182493180.jpg)
If you're stuck on the VMware boat, you can get ESX(i) working on a Mac Pro., but it seems to depend on which version Mac Pro you have. Why do you need a type-1 (bare metal) hypervisor? I think the best approach is running on Mac OS X. You can configure VirtualBox to run VMs in the background, independently of your login to Mac OS X and start them automatically at system boot. You can also write a script that freezes such background VMs before a Mac reboot. That's the configuration I use and it works well. I run a Linux and Win2008 server in the background and several VMs as applications in Mac OS.
VirtualBox is free and updated often. Plus you can transfer your VMs from the Mac host to Windows, Linux and Solaris hosts since VirtualBox runs on all four platforms.
The Hypervisor framework provides C APIs for interacting with virtualization technologies in user-space, without the need for writing kernel extensions (KEXTs). As a result, apps created using this framework are suitable for distribution on the Mac App Store. Hardware-facilitated virtual machines (VMs) and virtual processors (vCPUs) can be created and controlled by an entitled sandboxed user space process, the hypervisor client. The Hypervisor framework abstracts virtual machines as tasks and virtual processors as threads.