Introduction
Not all VPS are created equal: their characteristics depend heavily on the virtualization technology the provider uses. The two most common are KVM and OpenVZ. The choice between them directly affects performance, software compatibility, and price.
KVM: full hardware isolation
KVM (Kernel-based Virtual Machine) is built into the Linux kernel and turns the host into a hypervisor. Each virtual machine gets its own OS kernel, its own file system, and emulated devices.
Pros:
- You can install any OS: any Linux, *BSD, even Windows.
- Full control over the kernel: your own modules, any versions.
- Honest resource guarantees: vCPU and RAM are reserved.
Cons: slightly higher overhead (5–10%) and a higher price for the same amount of resources.
OpenVZ: container virtualization
OpenVZ splits one shared kernel among many containers. Isolation happens at the process level, not the hardware level.
Pros:
- Minimal overhead — performance is close to bare metal.
- Low price: the provider packs the host more densely.
Cons:
- Linux only, and only distributions compatible with the host kernel.
- You cannot load your own kernel modules.
- Resources are often "shared": a neighbor's spike can affect you.
Analysis: comparing the technologies
| Criterion | KVM | OpenVZ |
|---|---|---|
| Isolation type | Hardware (hypervisor) | Container (shared kernel) |
| OS choice | Any, including Windows | Linux only |
| Custom kernel modules | Yes | No |
| Performance | ~90–95% of bare metal | ~98–100% of bare metal |
| Resource guarantee | Hard | Soft (often oversold) |
| Price at equal limits | Higher | Lower |
| Suitable for VPN/tunnels | Yes, any protocol | With limitations |
Analysis conclusion. For serious tasks — your own VPN server, databases, Windows applications — KVM has no alternative: isolation and compatibility matter more than 5% of performance. OpenVZ makes sense for lightweight sites, tests, and bots where price is critical. All else being equal, paying extra for KVM is paying for predictability: you don't depend on the host kernel or on your neighbors' appetite.
Bottom line
Look not only at the plan's numbers but also at the virtualization technology. The formula is simple: need control and reliability — go KVM; need maximum bang for the buck for a simple task — OpenVZ will do.