refurbished is good enough
To build my 3 node Proxmox Cluster I ordered three refurbished Lenovo ThinkCentre M720q.
Three laptop-sized boxes containing the proxmox minipcs
One of the ThinkCentre
All of the three ThinkCentre of the proxmox cluster
And yesterday I did at least managed to install basic proxmox, with ZFS as filesystem. As