Host: Debian 6.0 (squeeze) with qemu-kvm and libvirt from squeeze-backports ii qemu-kvm 1.0+dfsg-8~bpo60+1 ii libvirt-bin 0.9.8-2~bpo60+2 Has 3TB sata drives with software raid and lvm. It has a sequential write speed of ~140MB/s measured with dd bs=1M count=512 if=/dev/zero of=test conv=fdatasync Elevator set to cfq Guest Debian 6.0 (squeeze) Uses LVM as storage. Drivers are virtio and cache='none' Sequential write speed is considerably slower with only 25-50MB/s Elevator set to noop I'm kind of running out of ideas for further tweaks but I'm sure that I/O speed should be much faster because many people are reporting almost native performance with lvm.