After creating a new virtual server (or restoring from an EXPORT datastore) I am able to change the network interface from rtl8139 to Virtio. However; I cannot change the disk. In the admin console going to Virtual Machines --> <virtual machine> --> Virtual Disks --> <disk> --> Edit gives a menu, but the only option I can change is "is bootable". Options like "Interface" are grey and cannot be modified.
seems to be fixed by http://gerrit.ovirt.org/#change,4262