OpenVZ Hosting refers to a Virtual Private Server created through OpenVZ operating system-level virtualization (OS Virtualization) technique. OpenVZ virtualization is based on the Linux kernel and Operating System. OpenVZ allows anyone to to run multiple isolated operating system instances (also called “Containers”) on single physical web server. Those instances are called Virtual Private Servers (VPS) or Virtual Environments (VEs). VPS is definitely more popular term however.

OpenVZ virtualization technique is the basis of the popular commercial virtualization software Virtuozzo Containers owned by Parallels Inc. OpenVZ is licensed under the GPL version 2. It is also supported and sponsored by Parallels. The company does not offer commercial support for OpenVZ however.

Unlike other familiar virtualization technologies like Xen or Kernel-based Virtual Machine, the OpenVZ requires requires both the host os on the underlying physical server and Virtual Private Servers which run on top (guest OS) to be Linux. The VPS users can use different Linux OS distributions in their virtual instances. The VPS users can not run Windows or MacOS for example on a Linux based OpenVZ host server. Such machine requires reboot if the virtual environment processes get I/O hangs.

There is a certain performance advantage of OpenVZ based VPS compared to other form of virtualization. OpenVZ website says that, there is “only a 1–3% performance penalty for OpenVZ as compared to using a standalone server”.

OpenVZ is not considered as a “true virtualization” but as a technique that creates isolated containers (like FreeBSD Jails does). Other virtualization technologies like Xen, Kernel-based VM or VMWare virtualize the entire underlying server and allow the users of the Virtual Machines to run Operating systems (OS) different from the one of the physical machine. OpenVZ uses a single patched Linux kernel and therefore can run only Linux. However because it doesn’t have the overhead that a hypervisor do, and that’s it is considered as quite fast and efficient. The disadvantage is that all VPS function with the kernel version of the underlying physical server. Among other advantages is easy to allocate the unused RAM to any of the virtual servers, something which is not possible with full virtualization techniques.

OpenVZ based server system and the host VPS use a common file system. Each VPS instance  is a directory of files which is isolated using chroot. The new versions of OpenVZ also allow the container to have its own file system. Any VPS can be cloned by just copying the files in one directory to another and creating a config file for the VPS.

To find out more about OpenVZ, please visit http://wiki.openvz.org/Main_Page.

Shared Hosting (or Shared Web Hosting) is a term in the Internet Hosting industry which refers to a number or Virtual Hosting accounts and websites hosted on one physical or virtual instance (server). Each virtual account has its own partition on the server in order to be separated from others. All those hosting accounts share the resources (processor, memory, bandwidth, software) of the underlying server. It can host thousands of websites.

Shared Hosting services is either name-based or IP-based. In IP-based virtual hosting each Shared account uses a dedicated IP address. The host server is configured with multiple physical network interfaces, or virtual network interfaces on the same physical interface. In name-based virtual hosting all Shared accounts on the server share a single IP address. In name-based hosting Web browsers request a resource from the web server of the host server using HTTP/1.1 which includes a certain hostname as part of the request. The host server uses this information to determine which web site to show the visitor.

Please note that term “Virtual Hosting” has nothing to do with “Virtual Private Server Hosting” (VPS, VPS Hosting, Virtual Servers ).