VMware Cloud on AWS provides an ability to specify cores to socket assignment while configuring vCPU resources of your VM. Accurately represent to the OS the underlying CPU topology of your physical server. As the number of physical cores on a physical socket on a server model used in VMware Cloud on AWS may vary from you on-premises configuration, we recommend to recheck cores to socket assignment using the following rule: If the VM isn’t wide, it should have only one virtual socket, if the number of vCPUs can only fit into two sockets, create two virtual sockets (not 2 cores per socket).

The following examples illustrates the rule:

  • For a VM with 24 vCPUs, running on an i3 server, the recommended configuration will be 12 cores/2 sockets (24 vCPUs > 18 physical cores on one physcial socket)
  • For a VM with 24 vCPUs, running on an i3en host, the recommended configuration will be 24 cores/1 socket (24 VM cores == 24 physical cores on one physical socket)

In VMware Cloud on AWS avoid VM CPU configurations with more than two virtual sockets – such configurations might negatively impact application performance.  Guest OS will not be able to effectively use the accurate cache topology information (since VMware Cloud on AWS hosts have only two physical sockets).

NOTE: VMware Cloud on AWS has the “autosizing of vNUMA” feature for a VM turned on. “Cores per Socket” setting is not taken into account while creating the vNUMA topology. If migrating from vSphere versions prior to 6.5, recheck the VM vNUMA configuration if modification to “Cores per Socket” was made.

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