Live migration from low CPU count host to high CPU count host

[devedse]

I currently have 2 Proxmox hosts:
1. Has 4 cores
2. Has 40 cores

What I would like to do is be able to live migrate a VM in between these hosts while still being able to use all CPU cores. For example, when the sun is down I'd run the VM on a low power host. When the sun comes up, I'd use solar power to live migrate it to a 40 core beast of a server and spin it up into full power.

Currently proxmox has a limitation where it's not possible to assign more CPU cores then the host has available.

TASK ERROR: MAX 4 vcpus allowed per VM on this node

Would it be possible to allow users to spin up a VM with more cores assigned to it then the host has?

 

[guruevi]

So while it is on the low power node, what CPU would the 5th+ CPU be scheduled on? You can use CPU hotplugging, but that only goes up, you can’t unschedule threads on a CPU. You can run 10x4CPU VMs or my suggestion would be to scale up/down with K8s, Swarm or Slurm, leaving the 4 cores for the management plane.