On Sun, 6 May 2012, Pasi Kärkkäinen wrote: > with "fork performance" I assume you're comparing Xen PV to KVM ? > Yes, PV has disadvantage (per design) for that workload, since the hypervisor > needs to check and verify each new process page table, and that has some performance hit. > For good "fork performance" you can use Xen HVM VMs, which will perform well for that workload, > and won't have the mentioned performance hit. I used both PV and HVM VMs. I don't have the details to hand at the moment, but KVM was superior to both. PV drivers where applicable. I have been running KVM for about 15 months now, with 30 VM's on one host and 38 VM's on another. It has been solid; no problems, but unfortunately I had problems with Xen. Steve