8 weeks of #VCAP – Section 3 scenario – CPU Affinity!

Thanks once again to Tom Verhaeg for this great scenario.

The voice team has recently setup Cisco Unity. The VoIP administrator sends you an e-mail. To comply with Cisco best practices, the Cisco Unity VM needs to have CPU affinity set. You really don’t like this, but the VoIP administrator and your boss insist. Make it happen……..

Damn, this really isn’t a fun thing to do. CPU affinity restricts a VM only to run on specific cores / processors that you specify. There may be some requirements for this (such as the above), but overall you shouldn’t do it. This breaks NUMA architecture, and more important, Fully Automated DRS! To support this, the DRS level should either be manual or partially automated.

The process itself isn’t that complicated. Edit the settings of the VM and go to the resources tab. Under advanced CPU, you find the option for CPU affinity.


If you do not see the Scheduling Affinity piece on a DRS-Cluster host, you are running DRS in fully automated mode. You can set DRS to manual for this VM by going to the cluster settings, and under DRS select Virtual Machine options. Set the DRS mode for this VM to either disabled, manual or partially automated.