A few days ago, I came across a couple of blog posts about how VMware Server won’t run on top of Hyper-V. Frankly, I’m amazed that any hosted virtualisation product (like VMware Server) will run on top of any hypervisor – I always understood that hosted virtualisation required so many hacks to work at all that if it saw something that wasn’t the real CPU (i.e. a hypervisor handling access to the processor’s hardware virtualisation support) then it might be expected to fall over in a heap – and it seems that VMware even coded VMware Server 2.0 to check for the existence of Hyper-V and fail gracefully. Quite what happens with VMware Server on top of ESX or XenServer, I don’t know – but I wouldn’t expect it to work any better.

Bizarrely, Virtual PC and Virtual Server will run on Hyper-V (I have even installed Hyper-V on top of Hyper-V whilst recording the installation process for a Microsoft TechNet video!) and, for the record, ESX will run in VMware Workstation too (i.e. hypervisor on top of hosted virtualisation). As for Hyper-V in VMware Workstation VM – I’ve not got around to trying it yet but Microsoft’s Matt McSpirit is not hopeful.

Regardless of the above, Steve Graegart did come up with a neat solution for those instances when you really must run a hosted virtualisation solution and Hyper-V on the same box. It involves dual-booting, which is a pain in the proverbial but, according to Steve, it works:

1. Open a command prompt and create a new [boot loader] entry by copying the default one bcdedit /copy {default} /d "Boot without Hypervisor"
2. After successful execution copy the GUID (ID of the new boot loader entry) including the curly braces to the clipboard.
3. Set the HyperVisorLaunchType property to off bcdedit /set {guid} hypervisorlaunchtype off [using] the GUID you’ve previously copied to the clipboard.

After this, you should now have a boot time selection of whether or not to start Hyper-V (and hence whether or not an alternative virtualisation solution will run as expected).