Most teams who call us about OpenStack should be running Proxmox, and we tell them so on the first call. It costs us the bigger engagement and it is still the right answer, because the wrong one here is expensive in a way that takes two years to show up.
OpenStack vs Proxmox is usually argued on features, and that argument ends in a tie that teaches you nothing. Both are open source, both run KVM, both cluster, both do live migration and high availability. CloudSpinx builds and runs both from Nairobi, for clients across Kenya and East Africa, and the line between them has never once been about features.
The question that decides it
Does anyone outside your platform team need to launch their own machines?
If no, you want Proxmox. Your team knows every VM by name, capacity requests arrive as messages, and a web console that shows you the whole cluster is exactly the right tool. Three nodes and you have working HA. Proxmox VE will be in production in a fortnight and the licence is optional.
If yes, you want OpenStack. Once a developer, a department or a paying customer needs to create an instance without asking you, you need projects, quotas, roles, tenant isolation and an API that behaves like a contract. Proxmox has no real answer to that. It has users and permissions, not tenancy, and every attempt we have seen to bolt multi-tenancy onto it with scripts has ended as a maintenance liability owned by one person who has since left.
That is the whole decision. Not scale.
Scale is the wrong axis, and it is the one everyone uses
"We are too big for Proxmox" is almost always wrong. Proxmox handles dozens of nodes fine. We run clusters carrying more VMs than some OpenStack clouds we have inherited, and the operational load is a fraction. Several of those inherited clouds are Red Hat estates facing their own migration, which is a harder problem than anything Proxmox will hand you.
Meanwhile a four-node OpenStack cloud is entirely reasonable if four nodes is what a real tenancy requirement needs. The private cloud costs still land differently, because three controllers carry no workload of yours regardless of how small the cloud is, but small is not the disqualifier people assume.
What actually scales badly is OpenStack with nobody to own it. The upgrade cadence is real: skip-level upgrades run between SLURP releases on the OpenStack release schedule, which is a manageable rhythm if someone is watching it and a rescue project if nobody is. Proxmox forgives neglect for longer. That is not an argument for neglect, it is an argument for being honest about who your team actually is.
OpenStack vs Proxmox in production: networking, storage, on-call
Networking is the sharpest split. Proxmox gives you Linux bridges, VLANs and an SDN layer that works well for a network somebody designed by hand. OpenStack with Neutron and OVN gives tenants self-service networks, floating IPs, security groups and load balancers they create themselves, which is a different product rather than a better one. If your networking requirement is "these VMs are on VLAN 40", Neutron is pure overhead.
Storage is closer than people expect. Both run happily on Ceph, and on both, putting your disks on Ceph is what makes hosts disposable and live migration boring. Proxmox additionally does ZFS local storage properly, which is genuinely useful at two or three nodes where Ceph is not yet worth it.
Then there is the part nobody puts in a comparison: what happens when it breaks at 21:00. Proxmox failures are usually legible from one web UI by an engineer who has seen a Debian box before. OpenStack failures are distributed across Keystone, RabbitMQ, Galera and Neutron, and reading them is a skill. This is the real cost difference between the two, and it is paid in salaries, not licences.
The decision, as we give it on the call
Twelve to a hundred VMs, one team, no self-service. Proxmox. Three nodes, Ceph if you have the network for it, done.
A department or a customer needs their own quota-bounded space. OpenStack. That is the requirement it was built for and nothing else in the open source world does it as completely.
You are selling infrastructure to other people. OpenStack, without much debate. Tenancy, quotas and a real API are your product, not your platform.
You are running from a VMware renewal and nothing else has changed. Proxmox first. It is the shorter migration, the smaller retraining bill, and you can move to an OpenStack private cloud later if a genuine tenancy requirement shows up. Migrating twice is cheaper than operating something you cannot staff.
Nobody will own the platform. Neither, unmanaged. Pick whichever fits the requirement above and put it under a support agreement, or you are buying a problem that surfaces in year two.
If you are between two of those, send us the shape of the estate and who needs to touch it. Get it scoped, or ask on WhatsApp at +254 713 403 044. We will tell you if the answer is the cheaper one.