During the rental of a virtual server, users often pay attention to the processor, the amount of RAM, or the type of storage, but no less important is the virtualization technology. It determines the level of isolation of the virtual server, available capabilities, performance, and support for various operating systems.
Among the most well-known virtualization technologies are OpenVZ, Xen, and KVM. They differ in their operating principles, resource allocation approaches, and levels of control over the server. Let's consider their main features.
Also read: How to choose a VPS
KVM — hardware virtualization with a high level of isolation
KVM (Kernel-based Virtual Machine) is one of the most widely used modern hardware virtualization technologies for VPS/VDS. It allows running different operating systems, including Linux, Windows, and BSD, with a high level of isolation between virtual servers.
Unlike container virtualization, this technology operates as a full-fledged hypervisor. Each virtual machine uses its own operating system kernel and receives isolated server resources — CPU time, RAM, disk space, and network resources. This gives the user more options for system configuration and a higher level of security.
The main advantages of KVM:
- support for various operating systems, including Linux, Windows, and BSD;
- high level of isolation between virtual servers;
- flexible resource and system configuration settings;
- good performance for websites, databases, and corporate services;
- convenient monitoring and management of virtual machines.
Today, KVM is considered one of the most popular and flexible solutions for VDS servers due to its combination of high performance, stability, and extensive customization options.
OpenVZ — container virtualization based on Linux
OpenVZ is a Linux-based container virtualization technology that has been actively used for VDS servers for a long time. Unlike KVM, it operates at the operating system level: all virtual servers use a shared Linux kernel but remain isolated from each other.
This approach allows for more efficient use of the physical server's resources and the ability to run a large number of VPS on a single host. Due to the lower load on the system, container virtualization provides good performance and lower costs for virtual servers.
The main features of OpenVZ:
- high density of VPS placement on a single server;
- efficient use of physical host resources;
- good performance for typical web projects and server tasks;
- support for Linux distributions only;
- lower level of isolation compared to KVM.
Due to the shared use of the Linux kernel, the administrator of the physical server has broader access to containers and processes, and some resources are shared between virtual environments.
Today, the classic OpenVZ is gradually being replaced by more modern solutions, but the container virtualization model itself continues to be actively used in various technologies.
Xen — a flexible paravirtualization and full virtualization system
Xen is one of the oldest and most well-known virtualization technologies that has been actively used for VPS/VDS and server infrastructure for a long time. It supports both paravirtualization (PV) and full hardware virtualization, allowing different operating systems to run depending on the server configuration.
In paravirtualization mode, the guest operating system is adapted to work with the hypervisor, which reduces the load on server resources and increases performance. However, not all operating systems support this approach.
If paravirtualization is not available, Xen can operate in full virtualization mode. In this case, the system uses the hardware capabilities of the processor to run virtual machines without modifying the guest OS.
The main features of Xen:
- support for paravirtualization and full virtualization;
- high level of operational stability;
- good isolation of virtual machines;
- effective distribution of server resources;
- support for various operating systems depending on the mode of operation.
Xen is considered a stable and proven solution for server virtualization. Although KVM is used much more frequently today, Xen is still applied in certain corporate and cloud infrastructures.
The choice of virtualization technology depends on the project's tasks, performance requirements, operating system support, and the level of isolation between servers. OpenVZ is suitable for lightweight Linux projects with minimal resource consumption, Xen is focused on stability and flexibility, while KVM provides maximum control and broad compatibility with modern OS. Therefore, before purchasing a VDS, it is important to consider not only the server specifications but also the type of virtualization on which the infrastructure operates.
At the same time, for projects with very high loads, specific security requirements, or the need for full access to the physical resources of the server machine, renting a dedicated server may be advisable. Unlike VPS hosting, a dedicated server does not use shared virtualized infrastructure and provides the client with all the hardware resources directly.