Finally! Running ESX as a VM inside a physical ESX host!

When you find a great blog post that you know from the first glance that it’s going to be big, you really find yourself dragged to refer to it even if you won’t add much.

Eric Gray from VMware, has finally done it! He showed us on his great blog,, how we can run ESX 4.0 as a virtual machine inside a physical ESX host. That’s right, not a VMware Workstation, but a real physical ESX server.

Any regular reader of my blog or a follower on Twitter knows that I’ve been trying to do that since I had my hands on ESX 4.0 starting from the early beta to the RC, but I had no luck doing that. As per Eric, it seems that the new GA build allows you to do this with a little bit configuration tweaks. Eric also mentioned that internally VMware has been running ESX as a VM inside ESX servers with a special build to achieve that.

Which leads me to the question I actually get from people when they know what I want to do: Why would someone need to do something crazy like this?

There are many reasons actually, but here is my personal favorite:
– I want to be able to create a fairly big and complicated ESX labs, and in the same time, I have a fairly huge CPU and memory resources on my existing physical ESX clusters.
– Running ESX on VMware workstation is great, but you are always limited to the amount of memory you’ve got on your PC/Laptop. 4GB or even 8GB won’t really allow you to do much.
– In the Workstation scenario you can’t keep your VMs running all the time, you will always have to shut them down to free up your resources.
– Having your ESX servers as virtual machines gives you extreme flexibility, starting from creating as much NICs/Networks as you want, all the way to creating your own libraries for deferent configurations. Imagine now doing that with VMware Lab Manager and the flexibility you can get for building/sharing these libraries with your peers.

Of course everything has its limitation, and one of the things that I can think of right away, is the fact that you won’t run some features like FT within a virtualized ESX server. I haven’t tried it obviously, but form the restricted CPU requirements for running FT, I don’t think it would work in this scenario.

However, I am as much excited about the GA release as many out there now, where I’ll finally be able to virtualize ESX 4.0. It’s worth mentioning also that, as far as I know, doing the same for other hypervisors is not possible, like Hyper-V or XenServer. So, thanks to Eric for bringing this to our attention, and to VMware for their great flexibility and open mind to allow people to do something great like this.

Share Button