But can it run Minecraft?

I have a little cluster of four Dell r815s, all of which have a few AMD Opteron 6320 CPUs. Plenty of cores, but they only run at 2.8 GHz. It's great for *almost* every server application I could ever dream of, but it sucks at running Minecraft servers since they largely use one thread. How can I optimize it?

Using Proxmox to run an Ubuntu server VM. I already set the CPU type to host and it still struggles to generate chunks :c