OpenVZ
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| Developer(s) | Community project, supported by Odin, Inc. |
|---|---|
| Initial release | 2005 |
| Repository | src |
| Written in | C |
| Operating system | Linux |
| Platform | x86, x86-64 |
| Available in | English |
| Type | OS-level virtualization |
| License | GNU GPL v.2 |
| Website | openvz |
OpenVZ (Open Virtuozzo) is an operating system-level virtualization technology for Linux. It allows a physical server to run multiple isolated operating system instances, called containers, virtual private servers (VPSs), or virtual environments (VEs). OpenVZ is similar to Solaris Containers and LXC.
While virtualization technologies like VMware and Xen provide full virtualization and can run multiple operating systems and different kernel versions, OpenVZ uses a single patched Linux kernel and therefore can run only Linux. All OpenVZ containers share the same architecture and kernel version. This can be a disadvantage in situations where guests require different kernel versions than that of the host. However, as it does not have the overhead of a true hypervisor, it is very fast and efficient.
Memory allocation with OpenVZ is soft in that memory not used in one virtual environment can be used by others or for disk caching. While old versions of OpenVZ used a common file system (where each virtual environment is just a directory of files that is isolated using chroot), current versions of OpenVZ allow each container to have its own file system.
The OpenVZ kernel is a Linux kernel, modified to add support for OpenVZ containers. The modified kernel provides virtualization, isolation, resource management, and checkpointing. As of vzctl 4.0, OpenVZ can work with unpatched Linux 3.x kernels, with a reduced feature set.
Each container is a separate entity, and behaves largely as a physical server would. Each has its own:
OpenVZ resource management consists of four components: two-level disk quota, fair CPU scheduler, disk I/O scheduler, and user bean counters (see below). These resources can be changed during container run time, eliminating the need to reboot.
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