[rodgerd]

NUMA can absolutely ping you in virtual servers, but without access to the hypervisor you'll never know why it's happening (JVMs straddling NUMA regions have caused me pain in the past, when the guest was split across memory regions).

[dfox]

The point is that kernel inside VM guest knows nothing about NUMA, so it cannot do any kind of NUMA optimizations hence such optimizations cannot hurt performance as they do not happen at all.

[rodgerd]

Actually, KVM can allow you to create NUMA domains inside the guest, for better or worse.