Hi, I have a older opteron based box - IBM x3655 which I recently upgraded for a second CPU. It now has 2 quad cores, and each has the same amount of Ram, running on OVM 2_2_2 I have enabled Numa via grub config and am not sure if it''s correctly detected or not. in xm info I see the following: host : waxh0012.xenhosts.de release : 2.6.18-128.2.1.4.37.el5xen version : #1 SMP Sat Apr 9 05:30:32 EDT 2011 machine : i686 nr_cpus : 8 nr_nodes : 1 cores_per_socket : 4 threads_per_core : 1 cpu_mhz : 2300 hw_caps : 178bf3ff:efd3fbff:00000000:00000310:00802001:00000000:000007ff:00000000 virt_caps : hvm total_memory : 8191 free_memory : 6495 node_to_cpu : node0:0-7 node_to_memory : node0:6495 xen_major : 3 xen_minor : 4 xen_extra : .0 This means my 2 sockets are considered one NUMA node and I need not worry? Maybe I was misunderstanding NUMA, but I had thought these two CPUs should each show up as a node. This is the CPU topology from XenPM. CPU core socket CPU0 0 0 CPU1 1 0 CPU2 2 0 CPU3 3 0 CPU4 0 1 CPU5 1 1 CPU6 2 1 CPU7 3 1 Most of my newer servers are of course something "NUMA-ish" too (i.e. 6100 / 6200 or Xeon E56xx) so it would be great to know I''m not misconfiguring the systems. (I have also read that Xen4 had a lot more fixes in this direction but Xen4 is no option yet since some of the super-new systems have problems running that) Can someone enlighten me a little? Florian -- the purpose of libvirt is to provide an abstraction layer hiding all xen features added since 2006 until they were finally understood and copied by the kvm devs.