The two VMs are running on separate SSDs (unassigned devices plugin) so I don't think the disks should be the problem. I have also tried running 3Dmark when only running one VM and the result is good, but when running on both VMs the same time it's not even close to the performance I get when running on one VM.

 

Your thought on that the PCI Express not running at optimal speed are interesting, how could I check that? I'm starting to give up on this, I don't know what else I can try to get this working so all ideas are interesting to me.

 

Sometimes I can play a game on both VMs with good performance for a short while but then suddenly at some point  they start to perform bad. Sometimes I can play a game on VM1 and directly when I start VM2 the performance is decreased. The behavior is not consistent. I have also noticed that unRAID becomes slow when this happens. Does anyone know how I should use the emulatorpin in cputune when running two VMs? Should the emulatorpin value be the same on both VMs?

This might sound stupid but if you access the nvidia control panel, what is the physics processor set to? This shouldn't have an effect but if it's set to cpu, and the cpu gets a little warm and throttles after a while, it may explain the issue.

I have a Windows 7 VM Media Center that will not work with any NETKVM driver past .100.  With the later driver versions, the VM will lock up when an Xbox 360 MCE is started.  I am suspicious of the virtio network driver.  Just as an experiment I set the network model to e1000 and Windows loaded the native Intel e1000 driver.  Everything works as expected.

 

I know this will sound off the wall, but you might try this.  In the VM xml files change:

    <interface type='bridge'>
      <model type='virtio'/>
  </interface>

 

to:

 

    <interface type='bridge'>
      <model type='e1000'/>
    </interface>

 

and see if that doesn't make a difference.

 

From what I understand, the e1000 emulated NIC gives performance on par with the virtio driver.