VMWare vNUMA – When and How to enable or disable

When NUMA is enabled , Applications and OS can leverage the NUMA functionality and performance might be increased if OS/Applications are NUMA aware

Terminology:

Wide VMS : Core = 1 Sockets: X
Non Wide VMS : Core >=2 Sockets:X

Manual NUMA : We need to understand the underlying physical NUMA and set sockets and cores accordingly
vNUMA : ESX will check the physical NUMA architecture and automatically creates vNUMA nodes for VM

Enable NUMA

Manual NUMA for Non Wide VMS
vNUMA for Wide VMS .

vNUMA is enabled , by default , only when vCPUS are more than 8. To enable vNUMA for vcpus less than 8 we have to configure setting numa.vcpu.min at VM level

Disable NUMA

When Hot add is enabled , NUMA for VMS will be automatically disabled.

Cons of NUMA/When we should not use
    
Some Operating systems won’t support more than 4 scokets in that case even though VM has 6 vCPUS OS see only 4 CPUS
Few application licensing is based on # of sockets.

References:

https://blogs.vmware.com/vsphere/2013/10/does-corespersocket-affect-performance.html
http://www.vsysad.com/2015/09/what-is-vnuma/
https://blogs.vmware.com/vsphere/2013/10/does-corespersocket-affect-performance.html?utm_source=longwhiteclouds

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