Ceph

In our QEMU/KVM example here:

http://ceph.com/docs/master/rbd/libvirt/

We tell people to use the ide bus for RBD devices. It appears that the ide bus is limited to a queue depth of 1 and can't do more than about 70MB/s and ~380 IOPs per volume. The virtio bus does not appear to have this limitation and is faster even at queue depths of 1. We've recorded single volume throughput in excess of 1.1GB/s. Given this, we almost certainly should revamp our examples to use virtio instead of ide.