Stick to 'Intel PRO/1000 MT Server (82545EM)' for every guest that can use it, even debian/nginx (6.0.6) blasts with it, I was using virtio for some time which does do what it suppose to do, lower cpu use and less virtualization overhead, but the performance s*cks. Posted at Nginx Forum: http://forum.nginx.org/read.php?2,235687,235702#msg-235702