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Proxmox VE vs OpenNebula vs OpenStack

Summary

Comparison of the three open-source private-infrastructure platforms in this knowledge base: Proxmox VE, OpenNebula and OpenStack. They are often weighed against each other but sit at different ambition levels, so the practical question is not "which is best" but "how much cloud do I actually need". Facts come from the refreshed topic pages (2026-09-25). For container-centric stacks, see the sibling Infrastructure Platforms Comparison (Docker vs Kubernetes vs OpenStack vs OpenNebula).

TL;DR

Proxmox VE OpenNebula OpenStack
What it is Hypervisor appliance: Debian + KVM/LXC + cluster stack in one product Cloud manager: central controller (oned) orchestrating KVM and LXC fleets Cloud OS: dozens of cooperating services (42 official project teams) for multi-tenant IaaS
Design center Per-node simplicity; a cluster of a few to tens of nodes managed as one unit One control plane over many hypervisors, including edge clusters Massive scale-out, many teams, many tenants
Tenancy Users, groups, pools and RBAC on one admin plane Groups, VDCs, quotas, self-service portal, federated zones Full multi-tenancy: domains, projects, quotas, per-project networks
Scale sweet spot A few to ~50 nodes per cluster (no explicit limit; 50+ reported); Datacenter Manager for many clusters Tens to hundreds of nodes (500 hypervisors certified per oned), edge fan-out, federation beyond Hundreds to thousands of nodes (Nova cells)
Current version 9.2 (2026-05-21; arm64 2026-08-05); PBS 4.2, PDM 1.1. PVE 8 reached EOL in 2026-08 7.4.1 (2026-09-10); 7.4 "Helix" 2026.1 "Gazpacho" (2026-04-01, SLURP); 2026.2 "Hibiscus" planned 2026-09-30
Storage story Ceph and ZFS built in; one plugin layer over LVM, NFS, iSCSI and PBS Datastore abstraction over Ceph, NFS, local disks, LVM SAN, NetApp and Pure Storage Cinder, Glance and Swift (or Ceph RGW): pluggable, many backends
Backup Proxmox Backup Server (dedup, encryption, live restore) is part of the family Built-in backup framework: Restic (incl. S3) and rsync; Veeam B&R (EE); OneBEX export interface Cinder volume backups, Freezer, or third-party tools
License / cost AGPLv3, every feature free; optional support EUR 120-1,100 per socket-year; Premium 24/7 support from 2026-10-19 Community Edition Apache 2.0; Enterprise Edition packages under a commercial subscription (base fee plus per-node fee, no public price list verified) Apache 2.0; free upstream, paid via distributions (Canonical, Red Hat, Rackspace and others) or self-support
Ops skill floor One admin can run it A small team can run it A platform team is expected
Best for VMware replacement, homelab to enterprise clusters, hyperconverged branches Sovereign, hybrid and edge clouds, AI/GPU factories, MSPs Multi-tenant IaaS, large enterprises, telco, public-cloud-style internal platforms

Layer Mapping

The confusion dissolves once the three are placed on an ambition axis rather than treated as peers.

flowchart TB
    subgraph L1["Layer 1 - hypervisor appliance (per-node product)"]
        PVE["Proxmox VE 9.2<br/>KVM + LXC + pmxcfs cluster + CRS<br/>Ceph/ZFS + PBS + SDN built in"]
    end
    subgraph L2["Layer 2 - cloud manager (one control plane)"]
        ONE["OpenNebula 7.4<br/>oned central controller (Raft HA)<br/>Sunstone portal, XML-RPC + gRPC<br/>edge + AI factory focus"]
    end
    subgraph L3["Layer 3 - cloud operating system"]
        OS["OpenStack 2026.1<br/>Nova/Neutron/Cinder/Glance/Keystone...<br/>RabbitMQ + MariaDB/Galera<br/>SLURP release train"]
    end
    HW["Commodity servers (KVM hypervisors)"]
    PVE --> HW
    ONE --> HW
    OS --> HW
    PVE -. "grows into: PDM 1.1, Cattle-and-Pets roadmap" .-> L2
    ONE -. "grows into: federated zones" .-> L3

All three run the same workloads at the bottom (KVM guests, Linux containers, Ceph). The difference is how much cloud (tenancy, self-service, quotas, multi-team operations) wraps around them.

Which One Should I Pick?

The flowchart condenses the verdict below; the weighted matrices show the same result numerically.

flowchart TD
    START["Private infrastructure need"] --> Q1{"Do many teams or business units<br/>need isolated tenants, quotas<br/>and self-service APIs?"}
    Q1 -->|"No"| Q2{"Need a cloud portal, VDCs,<br/>edge sites or GPU factory orchestration?"}
    Q2 -->|"No"| PVE["Proxmox VE<br/>virtualization cluster + PBS"]
    Q2 -->|"Yes"| ONE["OpenNebula"]
    Q1 -->|"Yes"| Q3{"Hundreds to thousands of nodes,<br/>OVN networking, LBaaS,<br/>bare metal as a service?"}
    Q3 -->|"Yes"| Q4{"Platform team available,<br/>or a vendor distribution acceptable?"}
    Q4 -->|"Yes"| OS["OpenStack"]
    Q4 -->|"No"| ONE
    Q3 -->|"No, tens to hundreds of nodes"| ONE

Architecture Comparison

Proxmox VE

The stack lives on every node: web UI and API (pveproxy, port 8006), daemons, storage plugins, and the corosync-replicated cluster filesystem (/etc/pve, capped at 128 MiB). There is no external controller to size or babysit: the cluster is the product. Config replication gives duplicate-ID protection and quorum-gated safety; HA is watchdog fencing plus the Cluster Resource Scheduler, which in 9.2 balances by dynamic load. The trade-off is a bounded management plane (thousands of guests, not tens of thousands) and corosync network discipline. Proxmox Datacenter Manager (1.1, 2026-05-28) adds a multi-cluster view on top.

OpenNebula

Deliberately centralized: one oned daemon holds the state and serves XML-RPC (:2633) and, since 7.2, gRPC (:2634). It is fronted by the Sunstone portal and by OneFlow, OneGate, OneForm and OneKS services. For HA, three or more front-ends run oned with a built-in Raft implementation: one leader serves the API behind a floating IP and followers replicate the database log. That is far simpler to reason about and troubleshoot than OpenStack's many services and queues. Hypervisors stay thin (KVM or LXC plus monitoring probes). Strengths: production in hours, NVIDIA GPU and fabric orchestration aimed at AI factories, edge fan-out through OneForm-provisioned clusters, OneDRS (ILP-based) load balancing, and OneSwap VMware migration.

OpenStack

A constellation: Nova (compute), Neutron (network), Cinder (block), Glance (images), Keystone (identity), Horizon (UI) and more, each an independent service with its own database schema, communicating over RabbitMQ. API services run active/active behind HAProxy on (typically) three controllers, with MariaDB/Galera and RabbitMQ quorum. That architecture buys true multi-tenancy, quotas, per-service HA and an unmatched integration catalogue, and it demands a platform team, release-train discipline (SLURP releases such as 2026.1 Gazpacho, with direct upgrades from 2025.1 Epoxy) and deliberate capacity engineering. The OpenInfra Foundation, which hosts OpenStack, joined the Linux Foundation in 2025; technical governance stays with the Technical Committee.

Operations Compared

Dimension Proxmox VE OpenNebula OpenStack
Deploy ISO per node, join cluster (hours) Packages or OneDeploy (Ansible) on the front-end and hosts (hours to a day) Deployment tooling (Kolla-Ansible, OpenStack-Ansible, OpenStack-Helm, vendor distributions): days to weeks
Upgrade apt plus a major-version guide; PVE 8 reached EOL in 2026-08, so 8.x nodes must move to 9 Front-end-centric upgrades (onedb migration tools in CE) SLURP skip-level upgrades between .1 releases; significant planning
Day-2 backup PBS integrated (dedup, live restore) Built-in backup jobs (Restic, rsync; Veeam in EE) Cinder backups, Freezer, or third-party
GUI Integrated per cluster; PDM across clusters Sunstone cloud portal Horizon (dense, less polished)
Skills Linux and virtualization admin Same, plus cloud concepts Linux, Python services, messaging, databases and deep networking
Break-glass Everything is plain text under /etc/pve Central database and config: one place to look (oned.log) Per-service debugging across the constellation
Vendor support Proxmox subscriptions; global 24/7 for Premium from 2026-10-19 (Standard in a Q4 2026 window) OpenNebula Systems EE subscription (Elemental, Standard, Premium tiers) Distribution vendors or managed-cloud providers

Networking and Tenancy

  • Proxmox VE: Linux bridges and VLANs plus SDN (zones such as Simple, VLAN, QinQ and EVPN; WireGuard and BGP fabrics in 9.2). Tenancy is RBAC and pools within one admin plane.
  • OpenNebula: virtual networks over Linux bridge, 802.1Q VLAN, VXLAN or Open vSwitch (SR-IOV switchdev in 7.4), with security groups and virtual routers. Multi-tenancy uses groups and VDCs. Remote clusters on cloud or bare-metal providers are provisioned with OneForm; the legacy ec2/azure hybrid (bursting) drivers were removed in 7.0. Federated zones share users, groups and ACLs.
  • OpenStack: Neutron is the deepest of the three: full overlay networking (Geneve or VXLAN with ML2/OVN or ML2/OVS), Octavia load balancers, QoS, tenant routers and OVN BGP (2026.1). It is the price of running a network OS inside your cloud.

Decision Matrix

Dimension Proxmox VE OpenNebula OpenStack
Architecture Monolithic per-node cluster stack Centralized controller with Raft HA, thin nodes Distributed service constellation
Performance Near-bare-metal KVM; CRS balancing Thin hypervisor path; OneDRS balancing Good; more layers per request
Operations Simplest (one product) Simple (one controller) Most complex (platform team)
Cost Free; EUR 120-1,100 per socket-year for support Free CE; EE subscription for extra fixes, LTS and SLA support Free upstream; distribution support or self-support economics
Security Tight surface (management plane is the product; corosync isolation; 2FA, RBAC, OIDC) Controller is the crown jewel; standard hardening Keystone RBAC plus per-service policy: strong, but a wide surface
Ecosystem PBS, PDM, community Terraform/OpenTofu and Ansible providers, large community GPU, edge and hybrid focus, gRPC, OneSwap VMware migration Largest: drivers, vendor distributions, public-cloud-parity features
Scale ceiling No explicit node limit; 50+ node clusters reported; pmxcfs 128 MiB config cap 500 hypervisors certified per oned (users report ~2,000); federation beyond Thousands of nodes, many tenants
Lock-in risk Low (plain-text config, open API, portable images) Low (Apache 2.0 CE, open formats); some integrations EE-only Low per se; distribution and deployment-tool gravity

Weighted Decision Matrix

Scores (1-5) are editorial judgments based on the facts above, and the weights are illustrative. Change both to match your own priorities.

Scenario A: replace VMware for an internal platform of 5-20 nodes, one infra team, mixed VMs and some GPU.

Criterion Weight PVE OpenNebula OpenStack
Operational simplicity 25% 5 4 2
Time to production 15% 5 4 2
Backup/DR story 10% 5 3 3
Cost (license + support) 10% 5 4 3
Self-service/tenancy needs 10% 2 4 5
Scale headroom 10% 3 4 5
Ecosystem/talent 10% 4 3 4
GPU/AI features 10% 4 (passthrough, NVIDIA vGPU) 5 (GPU fabric orchestration) 3
Weighted total (max 5.00) 4.30 3.90 3.10

Scenario B: multi-tenant platform for several business units, 200+ nodes. Self-service and scale dominate; Proxmox VE scores lower on scale headroom because 200+ nodes means several clusters joined only by Datacenter Manager.

Criterion Weight PVE OpenNebula OpenStack
Operational simplicity 10% 5 4 2
Time to production 5% 5 4 2
Backup/DR story 5% 5 3 3
Cost (license + support) 10% 5 4 3
Self-service/tenancy needs 30% 2 4 5
Scale headroom 25% 2 4 5
Ecosystem/talent 10% 4 3 4
GPU/AI features 5% 4 5 3
Weighted total (max 5.00) 3.20 3.90 4.05

The two matrices nearly mirror each other, which is the point: these platforms win at different altitudes, and OpenNebula is the consistent middle.

Verdict

  • Proxmox VE when the requirement is a virtualization cluster, not a cloud: one team, tens of nodes, enterprise backup in the box, and VMware-exit pressure. It is the fastest path from decision to production and has the lowest operational floor. Moving to a cloud layer later is non-destructive: images port and PBS restores anywhere.
  • OpenNebula when those nodes must behave like a cloud (self-service portal, groups and VDC tenancy, edge sites, GPU factories with NVIDIA fabric orchestration) but a platform team for a full constellation is not available. It is the deliberate middle: much simpler than OpenStack, considerably more cloud than a hypervisor cluster.
  • OpenStack when multiple business units need isolated tenants with quotas and self-service at serious scale, when public-cloud-parity networking (OVN, Octavia) or bare metal as a service (Ironic) is required, or when a vendor distribution is acceptable to carry the operational load.
  • Sequencing: these are stages, not rivals. A common and defensible path is Proxmox VE now, then OpenNebula (or OpenStack through a distribution) when self-service demand arrives.

Sources

Facts align with the vault topic notes, checked 2026-09-25: Proxmox VE, OpenNebula, OpenStack. Per-topic primary sources are listed there.