Opensource components and services
 


Components of open source virtualization usually includes, hypervisor and tools for management and optimization.

An example of Xen is illiustrated as

The basic components of a Xen-based virtualization environment are the Xen hypervisor, the Domain0, any number of other VM Guests, and the tools, commands, and configuration files that let you manage virtualization. Collectively, the physical computer running all these components is referred to as a VM Host Server because together these components form a platform for hosting virtual machines.

The Xen Hypervisor

The Xen hypervisor, sometimes referred to generically as a virtual machine monitor, is an open-source software program that coordinates the low-level interaction between virtual machines and physical hardware.

The Domain0

The virtual machine host environment, also referred to as Domain0 or controlling domain, is comprised of several components, such as:

  • The SUSE Linux operating system, which gives the administrator a graphical and command line environment to manage the virtual machine host components and its virtual machines.

    [Note]  

    The term Domain0 refers to a special domain that provides the management environment. This may be run either in graphical or in command line mode.

  • The xend daemon (xend), which stores configuration information about each virtual machine and controls how virtual machines are created and managed.

  • A modified version of QEMU, which is an open-source software program that emulates a full computer system, including a processor and various peripherals. It provides the ability to host operating systems in full virtualization mode.

Xen-Based Virtual Machines

A Xen-based virtual machine, also referred to as a VM Guest or DomU consists of the following components:

  • At least one virtual disk that contains a bootable operating system. The virtual disk can be based on a file, partition, volume, or other type of block device.

  • Virtual machine configuration information, which can be modified by exporting a text-based configuration file from xend or through Virtual Machine Manager.

  • A number of network devices, connected to the virtual network provided by the controlling domain.

Management Tools, Commands, and Configuration Files

There is a combination of GUI tools, commands, and configuration files to help you manage and customize your virtualization environment.


The following graphic depicts a virtual machine host with four virtual machines. The Xen hypervisor is shown as running directly on the physical hardware platform. Note, that the controlling domain is also just a virtual machine, although it has several additional management tasks compared to all other virtual machines.

Figure 1.1. Virtualization Architecture

Virtualization Architecture

On the left, the virtual machine host’s Domain0 is shown running the SUSE Linux operating system. The two virtual machines shown in the middle are running paravirtualized operating systems. The virtual machine on the right shows a fully virtual machine running an unmodified operating system, such as Windows Server 2003 or Windows XP.