We have been using Proxmox for a while now, the server we have is however slowly filling up. To solve this we have aquired more servers to run Proxmox on. We have been reading into clustering and have concluded this is very interesting for us to make managing and migrating the machines easier, so we made a cluster from the two new servers and subsquently wanted to add the existing server to this newly created cluster. We quickly found out this cannot be done. So now I have a cluster (non production, at the moment) that contains the two new servers and a single standalone server (production). I want all the proxmox machines in the same cluster and doing anything drastic to the production server is out of the question as far as I am concerned. What would be the best way to go about this? Do I create a cluster on the production server and add the new servers to that? Can I do that with them already beeing a (members of) a cluster? (e.g. can i break down the existing cluster?) or do I really need to re-install the new machines? Is this even the correct way of going about this? Any tips are appreciated!