>So why is ovirt's guest disc performance (native and gluster) so poor? Why is it consistently giving me about 1/10th to 1/80th of the hosts disc throughput?

About the glister cluster volume  - try without sharing. I have tested glusterfs (fuse Mount) with tmpfs and the maximum throughput was 55 MB/s on the host and 20MB/s on guest. Disabling sharing increased the write performance on the hosts, while minimum performance on the VM.

Now I use storhaug, ctdb & nfs-ganesha. Write (sequential)  performance in the guest jumped to 80MB/s which is OK for a gigabit network.

!!!Keep in mind that stopping sharding destroys everything!!!

Also configure your VMs to use write back (an option in custom section), which could be potentially risky - but I have never lost a VM until now ( used standalone KVM with 4 disk in software raid0) . Just keep write barriers ON, if you don't have a battery-backed write cache.

P.S.: I thing that glusterfs-gnfs packages are still unavailable for oVirt 4.3 . Maybe Greg can provide an update.

Best Regards,

Strahil Nikolov