Chapter 7. Xen and the Beauty of Virtualization

Derek Murray

Keir Fraser

 Principles and properties Structures
VersatilityModule
 Conceptual integrityDependency
Independently changeable Process
 Automatic propagation Data access
 Buildability  
Growth accommodation  
 Entropy resistance  

Introduction

Xen is a virtualization platform that has grown from an academic research effort to become a major open source project. It enables its users to run several operating systems on a single physical machine, with particular emphasis on performance, isolation, and security.

The Xen project has had great impact in a variety of fields: from software to hardware, academic research to commercial development. A large part of its success is due to it being released as open source, under the GNU General Public License (GPL). However, the developers did not simply sit down one day and decide to write an open source hypervisor. It began as part of a larger—and even more ambitious—research project called Xenoservers. This project provided the motivation for developing Xen, so we’ll use it here to explain the need for virtualization.

Making Xen open source not only made it available to a vast range of users, but also allowed it to enjoy a symbiotic relationship with other open source projects. The unique thing about Xen is that, when it was first released, it employed paravirtualization to run commodity operating systems such as Linux. Paravirtualization involves making changes to the operating systems that ...

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