Introduction

In Chapter 1, we reviewed the origins and theory behind virtualization. Various systems have been developed to subdivide, or virtualize, resources of a single physical computer. These systems exist on a wide variety of platforms. Some are dedicated to a particular hardware platform and guest operating system, while others can be installed on a variety of architecture and support a diverse selection of guests. Their approach varies, but they all share one goal: to assist with high levels of consolidation, increase server utilization, and enable rapid provisioning of partitions to meet your business needs on demand. Xen has been proven to accomplish all that, and has been very successful in doing so.

With its root in open source, and with heavy development still coming from the open-source community, Xen is posed to be one of the most popular and widely used virtual machine monitors (VMMs) for its supported platforms. Many operating systems are integrating Xen s hypervisor into the operating system itself; soon it will not be necessary to even install Xen to begin achieving greater efficiency in your data center. However, Xen is much more than just another free VMM. XenSource, the company currently leading ongoing development efforts of the VMM, has brought Xen into the commercial limelight as a viable solution for the enterprise data center.

This chapter will discuss Xen in detail, including the open-source release as well as the commercial variants from XenSource XenExpress, XenServer, and XenEnterprise. We will illustrate the underpinnings of the product as well...