XenDesktop 5.5 on Hyper-V and BSOD 0x0000007B

Something you do not want to see at 4pm on a Friday!  But this is what I saw…

BSOD after upgrading PVS vDisk image

What had prompted this was a simple change within my PVS Windows 7 image, increasing the Page File size and rebooting.  Every time the PVS image got to the Starting Windows screen, it would blue screen and then restart. 

This was using XenDesktop 5.5, PVS 6.0 and Windows Hyper-V.

Luckily for me, this was not an image corruption as I tested the following:

  • Removed the virtual machine cache disk and then added both the Windows 7 image and the vDisk cache back to the virtual machine as two separate virtual disks. 
  • Removed the Synthetic NIC (leaving only the Legacy NIC).
  • Changed the boot order from network to Hard disk.

I was now able to boot the virtual machine from the image disk, proving it wasn’t corrupted.

Now, here is the good bit.  The cause of the problem is a known issue with the way we offload the PVS NIC connection to the Synthetic NIC (for further information see Page 11 Network Consideration XenDesktop with Microsoft Hyper-V Design Guide http://support.citrix.com/article/CTX124687

Once the vDisk had loaded and I’d logged on, if I went to the properties of the Network Adapters, I saw the following:

Incorrect NIC Adapter settings

Now, the problem is that the Citrix Network Lightweight Filter should be the other way around, being applied to the PVS (Legacy) NIC and not applied to the LAN (Synthetic) NIC – like this! 

Correct NIC Adapter settings

During the upgrade and reseal of the PVS image, these settings swapped over and caused the BSOD.  By powering up the VM, booting from the vDisk and not the network (proving it was PVS and not the image), we are able to put these settings back to how they should be, reseal the image and voila… all is good again.

I would like to thank Simon for this, as it was he who showed me this fix but I thought I would share it on his behalf!  Thanks for getting me out of trouble on Friday afternoon!


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