Calculate minimal resources needed

I played a bit around, seems OK - nice job!

What I'd maybe add is a RAM cost for the Proxmox VE node itself, default to say, 1GB. This way one can also easily simulate having ZFS with an ARC-Size of X GB. Possibly also a multiplicator for how many vCPUs can share one CPU, just as idea.
But, I mean that's pretty easy to figure out from the raw reserves.