OpenVZ vs KVM
How OpenVZ and KVM Virtualize a VPS
OpenVZ vs KVM is a comparison of two ways to build a virtual private server. OpenVZ uses operating-system-level virtualization, where each VPS is a container that shares the host's Linux kernel. KVM uses full virtualization, where each VPS is a virtual machine with its own virtual hardware and kernel.
With OpenVZ, all containers run on one kernel, so the host decides which kernel version every customer gets. Each container still has its own files, users, processes and network view, so it looks like a separate server from the inside. With KVM virtualization, the hypervisor presents virtual hardware to each guest, and each guest boots its own operating system and kernel. Containers in general are covered in containers vs virtual machines.
Kernel Control, Isolation and Resource Guarantees
The shared kernel is the biggest practical difference. A KVM customer can install a different kernel, load kernel modules or run another operating system family. An OpenVZ customer cannot change the kernel, so software that needs specific kernel features or modules may not run at all.
Isolation differs too. In a KVM guest, the hypervisor enforces the memory and CPU assigned to it, and a crash in one guest does not bring down the others. In OpenVZ, all containers depend on the same kernel, so a kernel-level failure affects every container on that host.
Resource limits follow from this design. KVM gives each guest a clearly defined allocation of virtual CPU, memory and disk. OpenVZ sets limits inside a shared kernel, which allows more containers per server, but what each one actually receives depends more on what its neighbors are doing.
Choosing Between the Two for a Real Workload
A developer wants a test server that runs a newer kernel and a container engine that needs extra kernel features. An OpenVZ container will usually refuse those changes, so the developer chooses a KVM plan, where the server behaves like a normal Linux machine.
A small business runs a brochure website and a mail forwarder, both light workloads. Either type of VPS can handle that, so price, support and the provider's track record on uptime matter more than the virtualization type.
Because OpenVZ containers share a kernel and can be packed densely, providers have often used them for low-cost plans. Such plans frequently rely on overselling, so check the guaranteed resources before you buy.
Frequently asked questions
Is OpenVZ still a good choice for a VPS?
For most buyers, KVM is the safer default. It gives each server its own kernel, clearer isolation and fewer restrictions on software. OpenVZ can suit simple, light workloads on a tight budget, but read the resource terms carefully and confirm that your software runs in a shared-kernel container.
Can I run Docker on an OpenVZ VPS?
It is often restricted or unreliable. Docker depends on kernel features such as namespaces and control groups, and an OpenVZ container can use only the features the host kernel makes available to it. A KVM VPS has its own kernel, so Docker usually runs there without these limits.