On Mon, 2009-11-09 at 10:18 +0100, Mathieu Baudier wrote: > > I selected one virtual CPU for the XP load...primarily because I want to > > run a couple more VMs and the guidance was to allocate one real CPU per > > VM. > > My understanding is that Win XP will perform a fundamentally different > install depending on whether it detects 1 or many CPU. So if you ever > plan to reuse your VM with many CPUs, you should install it with many > right away (and follow the tip above: install as Windows Vista, not > XP). > > I had this problem with a Win XP VM that I installed with pre v3.0 > versions of VirtualBox: after VBox introduced SMP I could not use the > multi-processor feature since XP had been installed with one > processor. > > Anyhow, now that I'm using KVM, for my test desktop VMs I tend to > allocate a total of CPUs across the VMs higher than the number of my > physical CPUs, since they rarely need CPU power at the same time but I > want them to be able to run very smoothly if needed. > > > run a couple more VMs and the guidance was to allocate one real CPU per > > Which guidance are you talking about? In the Red Hat 5 Virtualization documentation it seems to strongly recommends having at least one physical cpu per VM. Since I have a quad core and I want to run the host plus 2-3 VMs, I decided give each VM one virtual cpu. Maybe I was too cautious. Dave