vNUMA (virtual NUMA)

vNUMA (virtual non-uniform memory access) is a memory-access optimization method for VMware virtual machines (VMs) that helps prevent memory-bandwidth bottlenecks. 

The vNUMA hypervisor creates a NUMA topology that closely mirrors the underlying physical server topology, allowing guest operating systems to intelligently access memory and processors. A VM's vNUMA topology will mimic the topology of the host on which it starts; this topology does not adjust if a VM moves to a different host.

Virtual NUMA is especially useful with large, high-performance virtual machines or multiple VMs in a vApp. With vNUMA awareness, the VM's memory and processing power are allocated based on the underlying NUMA topology even when it spans more than one NUMA node. vNUMA-aware VMs must be hardware version 8 or newer and operate on vSphere 5.0 or newer, with NUMA-enabled hardware. 

If a VM has more than eight vCPUs, vNUMA is automatically enabled. The VMware admin can adjust virtual NUMA topology for a VM, or enable vNUMA awareness on a smaller VM, using advanced configuration settings.VMs using many virtual CPUs (vCPUs) are more likely to access more than one NUMA node (local memory tied to a processor) on the underlying physical server.