When a VPS is advertised, the virtualisation type — KVM or OpenVZ (and its modern descendant, container-based virtualisation) — tells you more about what you are really getting than the RAM figure does. The difference is isolation: KVM is a full virtual machine, OpenVZ is a container sharing the host’s kernel. That one distinction drives everything else.
KVM: a real virtual machine
- Own kernel — you can load modules, run any OS (including Windows and BSD), and use Docker or nested virtualisation.
- Dedicated resources — allocated RAM is truly yours, not oversold against a shared pool.
- Strong isolation — a neighbour cannot see your processes or exhaust the host kernel from inside.
The cost is a little more overhead per VM, which is why KVM plans are usually priced slightly above equivalent containers. For almost every serious use case it is worth it.
OpenVZ / containers: shared kernel
- Shared host kernel — you cannot change kernel modules, and Docker or custom kernels may not work.
- Often oversold — “burstable” RAM can vanish when the host is busy, because it was never exclusively yours.
- Cheaper — lower overhead makes these the budget tier.
How to tell what you are running
If you are not sure which type a provider gave you, a couple of checks reveal it:
Run systemd-detect-virt — it prints kvm or openvz/lxc. On a container you also cannot load modules (modprobe fails), and free -m may show suspiciously round, host-wide numbers.
When the difference actually matters
- Docker, Kubernetes, nested VMs — need KVM. Containers usually cannot run them reliably.
- Custom kernel, VPN modules, some security tooling — need KVM’s own kernel.
- Guaranteed RAM for a database — KVM, so allocation is not oversold.
- A cheap always-on box for light tasks — a container can be fine, if you trust the host’s ratios.
The short verdict
Choose KVM unless you have a specific reason not to. The small price premium buys real isolation, guaranteed resources and the freedom to run anything. Every VMHeaven VPS is full KVM with dedicated resources — no shared kernel, no overselling, Docker and custom kernels welcome.
Frequently asked
Can I run Docker on an OpenVZ VPS?
Often not reliably — containers share the host kernel and cannot load modules or run nested containers. Docker, Kubernetes and custom kernels need KVM.
How do I tell which virtualisation my VPS uses?
Run 'systemd-detect-virt' — it prints kvm, openvz or lxc. On a container, modprobe fails and free -m may show host-wide numbers.
Is KVM worth the higher price?
For almost every serious use case, yes. The small premium buys real isolation, guaranteed (not oversold) resources, and the freedom to run any OS or kernel module.