Confusion over Multi-Processor Guest OS Support with Hyper-V

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After posting a link to our supported guest operating system list (https://support.microsoft.com/kb/954958/en-us) I have received a number of queries about the issue of multi-processor support.  You see, while we state that we only support Windows Server 2003 with up to virtual processors, and Windows Vista / XP with a single virtual processor - multiple people have let me know that they are running these operating systems with greater numbers of virtual processors, and are seeing no problems.

This is not surprising.

We have no idea what operating system you are going to run inside a virtual machine, and allow you to configure up to 4 virtual processors for any operating system you want.

The point of the support statement above is that these are the configurations that we have specifically tested, and will officially support.

Case in point - if you configure a Windows Server 2003 virtual machine with 4 virtual processors it will appear to correctly identify and utilize all 4 virtual processors.  However, as we have not formally tested this configuration and do not support it, if you encountered an issue while running in the configuration and needed to contact Microsoft product support - you would be asked to reproduce the problem with only 2 virtual processors first.

To summarize:

  • If you are running production / critical workloads - please stick to the supported list of operating systems / number of virtual processors.
  • If you are just playing around - feel free to try running greater than the officially supported number of virtual processors, but don't get mad at me if things blow up / fail in mysterious ways.

Cheers,
Ben