Are your Hyper-V Virtual Machines Locking Up?
7 March 2008I’ve been working recently with Windows 2008 Server and Hyper-V, trying to get my Virtual PC machines running under Hyper-V. One problem I kept running into is that at random times, my Virtual Machines would just lock up or freeze.
At first I suspected the conversion from the Virtual PC HAL to the new Hyper-V HAL and the new Hyper-V drivers. I fiddled around with the devices to no avail. It got so bad that a Virtual Machine locked up on me while installing a fresh copy of Windows 2003 Server Standard 64-bit. We’re talking it locked up in the DOS-like part of the installation. So something was up.
I double checked that the Dell Precision 390 I’m using as my server had the latest BIOS and host driver packages for the video and network adapters. I also verified that Intel VT-i extensions were enabled in the BIOS.
Finally after poking around in the settings for my Virtual Machines I discovered the one’s that were locking up all had their Virtual PC CPU Limit set to something other than “100″. Once I set all my Virtual PC’s to use one CPU and set their limit to “100″ they all became stable.
This might be a bug with the Hypervisor or the CPU, I’m not completely sure. I just know that when I set this value to “100″ all my Virtual Machines became stable and none of them locked up.
Just to clear things up, no other VM’s were ‘hogging’ CPU causing other VM’s to lock up due to resource contention. Of course I checked for this first 
Hope this helps someone else out!
Cheers!
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