I was talking to a customer a few days ago about their plans to use Hyper-V. One of their questions, that I wasn't expecting at all, was about the possibilities of running Hyper-V VMs inside of a Hyper-V VM. I knew there was some capability to run ESX inside of a VMware Workstation VM, but I didn't know about what happens with Hyper-V. So I ran a few tests to find out.

I used a PowerEdge R900 that already had Windows Server 2008 x64 with Hyper-V enabled. The first test was to try enabling the Hyper-V role inside of a 64-bit Windows Server 2008 VM. It failed with an error message that the processor didn't support hardware virtualization.

The next test was to try running Microsoft Virtual Server 2005 inside of a Hyper-V VM. I started with a 64-bit Windows Server 2008 VM and installed 64-bit Virtual Server 2005 R2 with SP1 inside that VM. I then was able to create a VM, but when I started the Virtual Server VM, it caused the Hyper-V VM that it was running in to reboot. I then tried to install the 32-bit version of Virtual Server inside the 64-bit Hyper-V VM and got an error during installation that the 64-bit version of Virtual Server was required because the host OS (THe 64-bit Hyper-V VM in this case) was 64-bit.

My final scenario was to create a new Hyper-V VM and install 32-bit Windows Server 2008. I then installed 32-bit Virtual Server 2005 successfully, and was able to create and start a VM. So this was success! The problem was that the performance was not very good. I tried to install 32-bit Windows Server 2003 in the new Virtual Server VM and after about two hours it was almost finished.

The conclusion was that this was not really a workable solution. In addition to the problems that I ran into, I am sure that it would not be supported.

The solution that I proposed to the customer was to use private virtual switches to create a set of VMs that were only accessible to each other and a "gateway" VM that was also connected to the "regular" network.

Todd