Sadly enough we never had more than 20+ concurrent spice connections and most of them were text consoles. In this case, our 40/10GbE link(s) were mostly idle.
That said, there's a vast difference between spice displaying VGA resolution and spice displaying 2K/4K resolution.
Hence my question about the type of VMs and by extension, the resolution used.
BTW, stupid question: Have you tried running iperf3 (or a similar tool) between your client machines and the oVirt cluster to verify that indeed you have 10GbE of usable bandwith?
- Gilboa