Question about NUMA Nodes per host in vSphere 5.5

[srikanthraavi]

16 NUMA Nodes per host in vSphere 5.5 what it means.. ?

Thanks

Message was edited by: a.p. - Changed the title from "Question"

[admin]

Hi,

NUMA non-uniform memory access is a Technology where you could group multiple CPU called as a node. so It means it will support 16 such groups made up of CPU's.

The below article should be helpful.

Understanding Non-uniform Memory Access

Thanks,

Avinash

[srikanthraavi]

Avinash,

       could you please elaborate still i am not clear.. what is main advantage..

Thanks

[UmeshAhuja]

Hi,

Most modern CPU’s, Intel new Nehalem’s and AMD’s veteran Opteron are NUMA architectures. NUMA stands for Non-Uniform Memory Access, but what exactly is NUMA? Each CPU get assigned its own “local” memory, CPU and memory together form a NUMA node. An OS will try to use its local memory as much as possible, but when necessary the OS will use remote memory (memory within another NUMA node). Memory access time can differ due to the memory location relative to a processor, because a CPU can access it own memory faster than remote memory.

ESX is NUMA aware and will use the NUMA CPU scheduler when detecting a NUMA system. On non-NUMA systems the ESX CPU scheduler spreads load across all sockets in a round robin manner. This approach improves performance by utilizing as much as cache as possible. When using a vSMP virtual machine in a non-NUMA system, each vCPU is scheduled on a separate socket.On NUMA systems, the NUMA CPU scheduler kicks in and use the NUMA optimizations to assigns each VM to a NUMA node, the scheduler tries to keep the vCPU and memory located in the same node. When a VM has multiple CPUs, all the vCPUs will be assigned to the same node and will reside in the same socket, this is to support memory locality as much as possible.

At this moment, AMD and Intel offer Quad Core CPU’s, but what if the customer decides to configure an 8-vCPU virtual machine? If a VM cannot fit inside one NUMA node, the vCPUs are scheduled in the traditional way again and are spread across the CPU’s in the system. The VM will not benefit from the local memory optimization and it’s possible that the memory will not reside locally, creating added latency by crossing the intersocket connection to access the memory.