Issues with adding a host to VMM when the computer has more than 16 processors
It has come to our attention that trying to add a computer with more than 16 processors (for example a quad six-core machine with 24 processors) is crashing the VMM server with the following exception:
System.InvalidOperationException: Nullable object must have a value.
From a Hyper-V perspective we support up to 24 cores (requires a QFE http://blogs.msdn.com/taylorb/archive/2008/09/23/24-core-support-for-hyper-v-hosts.aspx). We have a few workarounds for VMM to work in this case (either do #1 or implement #2 and #3):
- You can limit the number of CPUs via msconfig to 16 (we know this solution is not ideal in this case, but wanted to document it anyway)
- Go to BIOS, then navigate to Advanced Setup>Clustering Mode and set it to Physical (default is Logical)
- Use Bcdedit to add USEPHYSICALDESTINATION and set to YES. This forces the physical APIC to be used.