Even no of PVE nodes?

[proxwolfe]

If both qdev and 2 hosts are off, your cluster will have no quorum (Expected=5, votes=2). Your sentence should be more like "If the quorum device fails, there is no harm done, as long as at least three of the four real nodes are online."

Besides Proxmox quorum, you should keep in mind Ceph quorum: if two of your three monitors are down, all i/o is paused. Also, if not enough OSD are available to honor your min_size (typically 2), i/o will be halted too.

Yeah, I think you are right.

But then it doesn't work the way it needs to. I want one of the three 24/7 nodes to be allowed to fail (or go down for maintenance) and the cluster continue to work.

Maybe UdoB's idea could be the solution. Have to think that through.

 

[ole37]

So my plan was to have the fourth node join CEPH but not host any OSDs. If I also don't set ip up as Monitor or Manager? Would that keep it neutral in the quorum count?

I've not used CEPH, but if I understand it correctly, I think having a CEPH node which is not intended to be running most of the time would be a bad idea. It seems like this would be analogous to having a RAID array with one dead drive. Am I not understanding how CEPH works in this regard?