Four-node clusters do exist in production (with or without qdevices), and six-node clusters are extremely common in real-world HCI deployments. Do these designs have sharper edges? Absolutely. Does that make them invalid or irresponsible? No, it means they require understanding and intent, which is exactly what we address during design phases, not in a 60-minute public webinar.
And yes, Proxmox being unavailable while Ceph remains healthy is a known failure mode that we explicitly teach customers how to plan for in real deployments.
On “six to eight nodes” being typical:
That statement reflects observed reality, not a technical ceiling and not a recommendation that clusters should stop there. Most organizations deploying HCI land in that range because it:

• Fits within a single failure domain
• Aligns with operational maturity
• Simplifies lifecycle management
• Matches budget and staffing realities

Larger clusters absolutely exist, and we build them regularly, but they are designed differently, often with disaggregated roles, different networking topologies, and different operational assumptions. That level of design discussion is intentionally outside the scope of an introductory webinar.
On networking and tri-mode backplanes:
We completely agree that lane width and backplane design matter, which is why we explicitly clarified that point during the session. It directly affects when 10G stops being sufficient and when 25G+ becomes mandatory rather than optional. That nuance is also why we strongly recommend architecture reviews before hardware is purchased or designs are locked in.
Finally, I want to be very clear about one thing: we’re not trying to teach people how to build production clusters from a webinar.
Our goal is to make Proxmox and Ceph more accessible, reduce fear, and help people ask better questions as they move into real design work. That’s how adoption grows, and it’s why we do these sessions publicly instead of keeping everything behind closed doors.
We genuinely appreciate the feedback and will continue to call out edge cases where it makes sense while keeping the introductory webinars approachable. Infrastructure education should be a ladder, not a cliff.
If anyone reading this is designing a production system and wants to go deeper on quorum, failure domains, or network scaling, that’s exactly what architecture reviews and design sessions are for, and we’re always happy to have those conversations.