OpenNebula vs CloudStack: Which Virtualization Management Platform Should You Choose?

Apache CloudStack and OpenNebula are both well-known cloud and virtualisation management platforms for operating IT infrastructure and delivering Infrastructure as a Service (IaaS). Both support KVM virtualisation, multi-tenancy, isolated virtual networks and self-service provisioning. For infrastructure teams evaluating VMware alternatives following Broadcom’s licensing changes, both could be under consideration. Both sit in the same category: IaaS orchestrators, built to publish infrastructure to tenants who are not the operator. This article will give you a guided comparison between both and will help you make your choice if you are in evaluation.

By reading further you will get an understanding how each platform fits your infrastructure, your team and the services you need to deliver. Architecture, networking, automation, licensing and support all influence the work involved in deploying and operating a cloud. This CloudStack and OpenNebula comparison examines those differences and their practical implications for enterprises and service providers. Whether you are comparing both platforms for a new deployment or considering CloudStack as an OpenNebula alternative, it will help you identify what to assess before making a decision.

 

Comparing by Domain

Symbol	Description
●	Full, in the entry product with no extra purchase
$	Above baseline, needs a higher edition or a separate product
◐	Partial, there with a limitation that matters
○	Not covered.
ACS	Apache CloudStack
ONE	OpenNebula

Note: Assessed on Apache CloudStack 4.23.0.0 and OpenNebula 7.4 ‘Helix’ release notes.

 

Architecture

The clearest way to see the difference is to count what runs before you create your first virtual machine.

Capability	What it is	ACS	ONE
Control plane components	The services and appliances that must already be running before any tenant workload exists, and the memory and CPU they occupy at every site.	●	●
Control plane high availability model	Whether the management layer survives the loss of one of its own nodes without manual intervention, and by what mechanism.	●	●
Remote console architecture	How a tenant reaches the screen of a running instance, and whether that traffic passes through a dedicated appliance or the web layer.	●	●
Documented scale limits	Whether the vendor publishes a tested ceiling for hosts, instances and clusters per management domain.	◐	◐

A CloudStack Core Zone starts up with system virtual machines: a Secondary Storage VM for templates and snapshots, a Console Proxy VM for console sessions, and a Virtual Router per guest network for DHCP, DNS, NAT and firewalling. Each hypervisor host runs cloudstack-agent. An OpenNebula deployment starts with none of that: the oned daemon talks to hosts over SSH and drives libvirt directly, console access is proxied by FireEdge on the front end, and the only appliance it instantiates is a Virtual Router, and only when a network needs routing.

Neither approach is simply better. CloudStack’s system VMs isolate failure domains and let console and storage traffic scale independently of the management server, at the cost of components to patch and monitor. Edge Zones drop them entirely: a far-edge site runs a single KVM host with local storage, no secondary storage, no Secondary Storage VM and no Console Proxy VM. OpenNebula’s agentless model means fewer moving parts and a smaller footprint, at the cost of more load on the front end and a dependency on SSH reachability to every host.

The layering differs too. CloudStack models Region, Zone, Pod, Cluster and Host. OpenNebula has Cluster and Host, with Zone appearing only in federated deployments and no Pod at all.

Neither approach is simply better. CloudStack’s system VMs isolate failure domains and let console and storage traffic scale independently of the management server, at the cost of components to patch and monitor. Edge Zones drop them entirely: a far-edge site runs a single KVM host with local storage, no Secondary Storage, no Secondary Storage VM (SSVM) and no Console Proxy VM (CPVM). OpenNebula’s agentless model means fewer moving parts and a smaller footprint, at the cost of more load on the front end and a dependency on SSH reachability to every host.

The layering differs too. CloudStack models Region, Zone, Pod, Cluster and Host. OpenNebula has Cluster and Host, with Zone appearing only in federated deployments and no Pod at all.

 

Compute

 

Capability	What it is	ACS	ONE
Hypervisors supported as first-class drivers	Which hypervisors the platform manages directly, with full lifecycle control rather than one-way import.	●	◐
Bare metal provisioning through the platform	Whether physical machines can be provisioned as workloads through the platform, rather than only imaged as cluster nodes.	●	$
Containers managed alongside VMs	Whether Linux system containers run through the same objects, networks and storage as virtual machines.	◐	●
Live migration and live storage migration	Moving a running instance to another host, and moving its disks to other storage, without stopping it.	●	●
GPU passthrough and vGPU/MIG partitioning	Assigning a whole GPU to an instance, or partitioning one physical card so several instances share it.	◐	●
Importing / adopting pre-existing unmanaged VMs	Bringing a virtual machine already running outside the platform under its management, where it stands.	●	●
Instance sizing model	Whether instance shapes come from a catalogue the operator curates, or from values the tenant types in.	●	●

CloudStack manages KVM, VMware, XenServer and XCP-ng directly, with Hyper-V, Proxmox and MaaS arriving through the 4.23 extensions framework. OpenNebula 7.4 ships drivers for KVM and LXC; its vCenter driver was removed. Where CloudStack puts a service offering between the operator and the tenant, OpenNebula sets CPU and memory as template attributes, and has no disk offering at all.

Storage

Capability	What it is	ACS	ONE
Storage backends and protocols supported	Which storage systems and protocols can hold the disks of running instances.	●	●
Vendor array integration	Whether an array’s own features, including snapshots, replication and QoS, are driven by the platform or stop at the hypervisor.	●	$
Primary/secondary storage separation and cross-site snapshot copy	Whether running-disk storage is separated from image and snapshot storage, and whether a snapshot can be copied to another site.	●	●
Backup model	Whether backups capture only what changed since the last one, and whether a restore produces a running instance or a disk someone still has to assemble.	●	●
Tenant-facing object storage	Whether tenants get buckets they create and consume themselves, as distinct from the platform using object storage internally.	●	○
Disk QoS and whether it is delegable as a purchasable tier	Whether IOPS and throughput limits attach to something a tenant selects, rather than being set per machine by an administrator.	●	◐

CloudStack ships managed plugins for StorPool, Dell EMC PowerFlex, LINSTOR, NetApp ONTAP and SolidFire, Pure Storage FlashArray and HPE Primera. OpenNebula’s community edition covers Ceph, LVM, iSCSI and file datastores, with NetApp, PowerFlex and Pure Storage behind the subscription. Both throttle disk IOPS; the difference is that CloudStack puts the ceiling on an offering a tenant buys, while OpenNebula’s equivalent sits in the restricted-attribute list and stays an administrator’s control.

 

Networking

This is the domain where the two are furthest apart. Since 4.20 CloudStack can run isolated networks and VPCs in ROUTED mode, where the Virtual Router allocates an AS number and establishes BGP peering, giving tenants routable addressing instead of NAT. The trade is explicit: in ROUTED mode source NAT, static NAT, load balancing, port forwarding and VPN are unavailable. A CloudStack VNF template also declares the interfaces it expects and gets each wired to the right guest network on deployment, where OpenNebula’s marketplace VNF is an ordinary image with context variables. On hardware, CloudStack supports SR-IOV as PCI passthrough and OVS-DPDK; OpenNebula adds SR-IOV in switchdev mode and BlueField DPU offload.

Capability	What it is	ACS	ONE
Tenant network isolation	How one tenant’s network traffic is kept separate from another’s on shared physical infrastructure.	●	●
VPC / multi-tier networks with their own ACLs	Whether a tenant can build several connected networks under one routing domain, each carrying its own traffic rules.	●	○
Gateway services	Whether NAT, DHCP, DNS and firewalling are delivered to tenant networks, and by what.	●	●
Load balancing, including TLS/SSL offload	Whether the platform provides a load balancer, and whether TLS certificates terminate there instead of on every backend instance.	●	◐
VPN	Whether tenants get encrypted connectivity back to their own premises, and whether individual users can dial in.	●	○
Routed tenant networks / per-tenant BGP peering	Whether a tenant network can carry routable addresses advertised upstream, instead of sitting behind address translation.	●	○
IPv6 and dual-stack tenant networks	Whether tenant networks carry IPv6 alongside IPv4, and under what conditions.	●	●
SDN and external network provider integration	Whether an external network controller or physical device can be driven by the platform rather than configured beside it.	●	◐
Bandwidth QoS and whether it is delegable as a purchasable tier	Whether a bandwidth limit is part of something the tenant selects, rather than applied after the fact.	●	◐
Hardware-level networking	SR-IOV mode, DPU offload and user-space packet paths.	◐	●

 

 Multi-tenancy & Identity

 

Capability	What it is	ACS	ONE
Tenant hierarchy depth	How many levels of tenant the platform models, and whether a tenant can contain tenants of its own.	●	◐
Quota and resource limits	Whether consumption can be capped, and at which levels of the tenant structure.	●	●
Self-service portal for end tenants	Whether end tenants get an interface of their own, separate from the operator console.	●	●
Identity federation	Which external identity systems can authenticate users, and whether each tenant can point at its own.	●	◐
RBAC granularity and custom roles	How finely permissions divide, and whether roles beyond the built-in ones can be defined.	●	◐
API credential scoping, expiry, and two-factor authentication	What an API credential is allowed to do, for how long it stays valid, and what protects interactive login.	●	●

 

CloudStack has nested domains, accounts and projects; OpenNebula has flat groups, compensated by the Virtual Data Center, which binds clusters, datastores and networks to a group more cleanly than CloudStack’s explicit resource dedication. The identity models are inverted in an interesting way.

CloudStack scopes the provider to the tenant, so different tenants federate to different identity providers. OpenNebula keeps providers global and maps external groups onto its own, so membership flows from the provider rather than the tenant choosing one. Only CloudStack lets the tenant own that choice, and only CloudStack has HSM-backed key management.

 

Operations & Lifecycle

 

Capability	What it is	ACS	ONE
Upgrade model	Whether the management layer keeps serving requests while it is being upgraded.	●	◐
Maintenance mode and documented safe shutdown of the control plane	Whether there is a documented way to take the management layer out of service without risking in-flight work.	●	◐
Metrics and monitoring	What the platform exposes for monitoring, and whether dashboards ship with it.	●	●
Usage metering, accounting and showback/chargeback	Whether consumption is recorded per tenant in a form that billing can consume.	●	●
Workload placement and DRS-equivalent rebalancing	How instances are placed when created, and whether the platform rebalances the cluster afterwards.	●	●
Backup and disaster recovery of the control plane itself	Whether there is a documented way to back up and restore the management estate itself.	◐	●

Both rebalance, and the difference is what feeds it. CloudStack DRS computes cluster imbalance from the allocated metrics of the service offering; OneDRS optimises over observed usage with a linear programming solver. A cluster can look balanced by allocation while being badly balanced in practice. OpenNebula goes further with forecasting that nothing in CloudStack matches, predicting host and VM metrics five minutes and thirty days ahead and feeding those predictions back into OneDRS. On accounting, OpenNebula’s showback is built into oned, while CloudStack’s usage data comes from a separate Usage Server, which is more to run and is also what keeps that load off the management database at scale.

 

API and automation

Every CloudStack operation is an API command, the web console is just another client of that public API, and requests are signed with a key pair rather than carrying a session. The difference that shows up day to day is the job model: a long-running CloudStack operation returns a job ID the client polls, while OpenNebula returns no queryable identifier for most operations, so the client watches the object’s state through LCM_STATE. The first tells you whether your request succeeded; the second tells you what the object looks like now, which is a weaker thing to build a portal or a billing integration on.

Capability	What it is	ACS	ONE
Public API completeness	Whether the web interface calls the same API available to scripts, or a privileged internal one.	●	◐
API authentication model	How an API request proves who it is.	●	●
Asynchronous job model	Whether a long-running request returns an identifier the client can poll, or whether the client has to watch the object’s state instead.	●	◐
Infrastructure as code	Whether infrastructure-as-code tooling exists for the platform, and who maintains it.	●	●
Kubernetes	Whether the platform provisions Kubernetes clusters itself, and whether it plugs into the Cluster API standard.	●	●

 

Automation tooling is the one area where the two are close:

• Terraform: both projects maintain their own provider.
• Ansible: CloudStack through a community collection shipped in the Ansible distribution, OpenNebula through modules listed among its own integrations.
• Kubernetes Cluster API: CloudStack’s is maintained upstream under kubernetes-sigs, OpenNebula’s in its own organisation with a SUSE Ready certification for Rancher.
• CLI and reference: CloudStack has CloudMonkey for the command line, and the UI builds its own navigation from listApis, so what an operator sees is derived from the same API a script calls. OpenNebula has XML-RPC, a FireEdge REST layer and a gRPC API added in 7.2.

 

Extensibility

This is the area where the gap is widest, and it is the strongest argument in CloudStack’s favour today. This needs to be shorter and straight to the point. It is a word salad now. Please summarise in 2-3 paragraphs with some bullets.

Capability	What it is	ACS	ONE
Adding an unsupported hypervisor without modifying the platform’s source	Whether support for a runtime the platform has never heard of can be added without modifying its source.	●	●
Pluggable drivers for storage, network and authentication	Whether the storage, network and authentication subsystems accept drivers written outside the project.	●	●
Extensions as registered objects with their own RBAC and API surface	Whether an extension is a registered object with its own permissions and API surface, or a file placed on disk.	●	◐
Marketplace or curated template catalogue	Where the images and appliances tenants deploy come from, and who curates them.	●	●

 

Apache CloudStack: CloudStack 4.23 has an extensions framework with two extension types. An Orchestrator extension delegates VM lifecycle to an external system and is registered against a cluster. A NetworkOrchestrator extension handles guest network and VPC services and is registered against a physical network. An extension is an executable in any language: CloudStack passes it an action name and a JSON payload and reads JSON back. Proxmox, Hyper-V and MaaS ship as built-in examples. Administrators can define custom actions with typed parameters, validation and role-based access control, exposed through the UI and the API like any other operation.

The result is that a hypervisor CloudStack has never heard of can be added without touching its source. There is a working example of exactly that: an open source extension that manages Firecracker microVMs through CloudStack, with a host agent, pluggable storage backends, VLAN tagging over Linux bridges or OVS, mutual TLS and a VNC console bridge. Firecracker is a runtime CloudStack has no native support for, and adding it required no change to CloudStack itself.

OpenNebula: It is extensible too, but at a different layer. Every subsystem is a pluggable driver declared in oned.conf: VM_MAD for hypervisors, VN_MAD for networks, TM_MAD and DATASTORE_MAD for storage, AUTH_MAD for authentication, plus the market and hook drivers. The drivers themselves are scripts on disk that you can read, copy and replace. The scheduler is pluggable in the same way, and a 7.4 install ships three of them. For someone comfortable at that level, it is a clean and honest design.

What OpenNebula does not have is the management layer around it. There is no registered extension object, no UI for installing one, no custom actions surfaced through the API with their own permissions. Adding a driver means editing configuration on the front end and restarting the daemon. That is a different proposition from registering an extension and granting a role access to its actions.

Apache CloudStack Overview 

Strengths

• Manages vSphere, KVM, XenServer and XCP-ng together, with Hyper-V, Proxmox and bare metal through the Extensions Framework, so one control plane can span a VMware migration.
• Compute, disk and network offerings carry IOPS ceilings, bandwidth limits and GPU profiles, so an operator publishes a tier once and then delegates, meters and bills against it. Usage aggregation runs on its own server, which keeps that load off the management server and its database in large deployments.
• Multi-tier VPCs with ACLs, VPN, TLS-terminating load balancing, ROUTED networks with automatic BGP peering and a VNF template type are all platform objects a tenant can be given.
• Nested domains, accounts and projects model resellers under resellers; identity federates per domain; API keys are scoped and time-limited; key management integrates with an HSM.
• Maintenance mode, a documented safe shutdown and live patching of the Virtual Router make the control plane something you can operate under an SLA.
• One edition under Apache 2.0, with no capability reserved for a paid tier.

Weaknesses

• Slower to a first cloud than OpenNebula: hours for a test deployment, a project for a production Zone. That setup is the Zone and Pod structure that makes it operable at scale, and far simpler than OpenStack, but a small team feels it.
• System VMs and the hypervisor agent are extra components to patch, monitor and recover when they fail.
• Usage data comes from a separate Usage Server you deploy and maintain, so reaching chargeback takes more setup than OpenNebula’s built-in showback.
• The five-layer model is overhead for a single datacentre.
• DRS balances on allocated metrics rather than observed usage, and there is no forecasting.
• No gRPC API, and no VM memory encryption on the native KVM path. Neither is something an extension can add, because they are the API’s own protocol and the guest definition rather than orchestration.
• System containers and in-guest command execution are not shipped. Both are reachable through an Orchestrator extension and custom actions, but as something you build and maintain rather than a product feature.
• No NVIDIA NVLink or NVSwitch fabric management.

OpenNebula Overview

Strengths

• No agent on the hypervisor and no system VMs, so there is a smaller footprint, less to patch, and a front end with two nodes that comes up in an afternoon.
• The Virtual Data Center binds clusters, datastores and networks to a group cleanly, where CloudStack needs explicit resource dedication.
• Accounting and showback are built into oned, available out of the box.
• Forecasting of host and VM metrics over five-minute and thirty-day horizons, feeding OneDRS, which optimises on observed usage.
• Strong AI and GPU position: NVIDIA Fabric Manager for NVLink and NVSwitch, an integration with NVIDIA’s infrastructure controller, a Slurm appliance, and VM memory encryption.
• Ahead on hardware networking: SR-IOV in switchdev mode, BlueField DPUs and DPDK.
• LXC system containers, a gRPC API, in-guest command execution, automated hyperconverged Ceph, and OneFlow for multi-VM services with dependencies.

Weaknesses

• KVM and LXC only. The vCenter driver was removed and Firecracker support from 6.x is gone.
• Detects unmanaged guests but provides no import path in 7.4.
• No offering object between template and tenant. QoS controls sit in the restricted-attribute list, which makes them administrator settings rather than tenant-selectable tiers.
• No VPC object, no built-in VPN, no SSL offload, no platform-managed per-tenant BGP.
• Flat groups rather than nested domains, and no OAuth or OIDC driver.
• No tenant-facing object storage; S3 is a backup destination.
• NetApp, PowerFlex, Pure Storage and Veeam drivers are enterprise integrations outside the community edition.

 

CloudStack vs. OpenNebula: How to make your final choice?

Both platforms have clear strengths. OpenNebula offers a smaller management footprint, built-in showback, workload forecasting and specialist capabilities for AI infrastructure and hardware networking. CloudStack’s advantage is how it brings infrastructure management, tenant services and service delivery together.

For service providers and enterprises, that translates into several practical benefits:

• A staged path beyond VMware. Manage multiple hypervisors through one control plane while moving workloads at a pace that suits the organisation.
• Consistent services tenants can select. Publish compute, storage, network and GPU tiers with defined limits and permissions, supported by usage metering for billing.
• Integrated networking and tenant management. Deliver services such as VPCs, VPNs and routed networks, with nested tenant structures suited to customers, business units and resellers.
• Control across multiple sites. Use a common infrastructure hierarchy, API and operational model as the cloud expands.
• Access to the full platform. Apache 2.0 licensing makes commercial support a separate choice, with no paid edition required to unlock capabilities.

Choose CloudStack to build a cloud or manage a virtualization that grows with your business and keeps you in control.

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