Not every VPS is built the same way. The virtualization technology underneath decides how isolated your server is, which software you can run and how it performs. The two names you will see most are KVM and OpenVZ, along with LXC.
Two ways to build a virtual server
Full virtualization (KVM) gives each customer a complete virtual machine with its own kernel. The hypervisor splits the hardware, and your server behaves like a real computer.
Container virtualization (OpenVZ, LXC) shares the host's kernel among all customers. Each container sees its own files and processes but runs on the same kernel as its neighbours.
Side-by-side comparison
| KVM | OpenVZ / LXC | |
|---|---|---|
| Kernel | Your own | Shared with the host |
| Isolation | Strong | Weaker |
| Run Docker, WireGuard, custom kernel modules | Yes | Often limited or impossible |
| Run Windows | Yes | No |
| RAM guarantee | Fixed and reserved | Can be oversold ("burstable") |
| Overhead | Small | Smallest |
Why KVM is the safer choice
- You choose the software. Docker, VPNs, firewalls such as nftables and tools that load kernel modules work without asking permission.
- Real memory. The RAM you buy is assigned to your machine. Container hosts sometimes sell more memory than exists and hope customers do not use it all.
- Better isolation. A fault or attack in a neighbour's virtual machine is far less likely to touch yours.
- Any operating system. Linux distributions, BSD and Windows all run unmodified.
When containers still make sense
Containers start fast and waste little, which is why hosts use them for very cheap plans and why you use them inside your own VPS through Docker. They are fine for simple workloads that need nothing special from the kernel.
How to check what you have
systemd-detect-virt
lscpu | grep -i hypervisor
cat /proc/user_beancounters # exists only on OpenVZkvm in the first command means full virtualization. If the last file exists, you are on OpenVZ.
Frequently asked questions
Is KVM better than OpenVZ?
For most uses yes. KVM gives each VPS its own kernel and stronger isolation, so you can run any OS and Docker. OpenVZ shares the host kernel and is more limited.
Can I run Docker on OpenVZ?
Often not, or only with restrictions, because containers share the host kernel. KVM is the safer choice for Docker.
Is KVM more expensive?
Slightly, because resources are allocated more strictly, but the isolation and compatibility are usually worth it.