In vSphere 5 , we introduced vNUMA which allows interested guest operating systems to see that they are running on a NUMA (Non Uniform Memory Architecture) topology. For those not familar, here is a one-diagram NUMA explanation. As you can see, in the UMA case, the cost of accessing a particular memory address is the same regardless of which socket your program is running on. In the NUMA case, however, it does matter. With memory attached directly to each socket there can be significant performance penalties if an application gener ates large numbers of non-local memory accesses. The ESX hypervisor has been NUMA-aware for quite some time, making memory and CPU allocation decisions based on its full understanding of the topology...
