KVM vs OpenVZ vs LXC — Why the Virtualisation Type Matters

What separates KVM from container VPS: own kernel, swap, custom modules, Windows images, fair isolation. Why NovaVPS sells KVM only.

Le corps de l'article est en anglais. L'interface, le catalogue et la caisse sont traduits.

Containers vs virtual machines

OpenVZ/LXC are containers: every VPS shares the host’s kernel, and “RAM” is a pool with burst accounting that evaporates under load. KVM is a true virtual machine: a real kernel of your choice, real swap, dedicated memory the host cannot reclaim. The price difference is a few dollars; the difference in behaviour shows up exactly when your workload matters.

What KVM gives that containers cannot

• Any kernel: custom builds, BPF tooling, kernel modules ( WireGuard, DKMS drivers).
• Windows and BSD images — containers are Linux-only by design.
• Real swap — memory spikes degrade gracefully instead of hard-failing.
• Docker-in-VPS without restrictions, nested virtualisation on request, RAW sockets for packet tools.
• Honest RAM — 4 GB is 4 GB, not 4 GB shared with forty neighbours.

The failure modes of oversold containers

Classic OpenVZ symptoms: the host hits memory pressure and your process gets the OOM kill despite “your” usage being small; a kernel feature you need simply does not exist; iptables modules are missing. These are not provider bugs — they are the architecture. KVM removes the class of problem.