Saturday, 19 May 2018

vNUMA: VMware vSphere 6.5

In vSphere 6.5, changing the cores per socket value no longer influences vNUMA or the configuration of the vNUMA topology. The configuration of vSockets and cores per socket only affects the presentation of the virtual processors to the guest OS, done generally for guest OS licensing purpose. 

vNUMA will automatically determine the proper vNUMA topology to present to the guest OS based on the underlying ESXi host. 

For example, lets assume that we create a 4-vSocket virtual machine with 4 cores per socket (i.e. total of 16 vCPU) on a ESXi host that has dual-socket-16-core per socket. Prior to vSphere 6.5, vNUMA would have created 4 vNUMA nodes based on the cores per socket setting. 

As of vSphere 6.5, the guest OS will still see 4 sockets and 4 cores per socket, but vNUMA will now only create 1 vNUMA node for the entire virtual machine since it can be placed in a single physical NUMA node. 

This new disconnection of the cores per socket setting with vNUMA allows vSphere to determine the best vNUMA topology automatically in all circumstances.

In case you still want to revert to the earlier behavior in vSphere 6.0, use the advanced setting:

numa.FollowCoresPerSocket = 1

For more Information concerning vNUMA can be found in the following articles:

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