3 February 2009 : Virtualization Comparison

The purpose of the Forum was to compare various virtualization technologies. IT managers from several central London IT companies attended.


  • Lee Chisnall of DNUK introduced Virtual Iron, a management system which controls the Xen hypervisor.
  • Mark Adams, the Technical Manager at Campbell-Lange Workshop, showed Xen running on two machines. He used the set-up to migrate a running service between two Linux servers, and then did the same thing with a Windows 7 operating system.
  • James Tansley of Hamiltons provided an impromptu introduction to some aspects of the VMWare infrastructure management console.

Forum Notes

Campbell-Lange Workshop's February forum focused on a general discussion of server virtualization, which included a comparison of different approaches through both GUI-based proprietary interfaces and direct application through the command line.

Rory Campbell-Lange provided a brief introduction to virtualization and the key terms and concepts involved. The differences between native and hosted hypervisors were discussed, and some of the benefits and risks associated with virtual environments were also noted.

Virtualisation Presentation
A slide from Rory's presentation. Click to download.

Lee Chisnall from DNUK, a hardware and solutions supplier, demonstrated Virtual Iron, a graphical interface built on a Xen hypervisor. Through this interface Lee took the group through the set-up of a virtual machine, which took less than a minute. He demonstrated how the physical resources of the hardware can be allocated and shared across the virtual machines to improve hardware utilisation. Operating system instances can be rapidly provided through Virtual Iron by using pre-loaded ISO and virtual disk images.

The Xen hypervisor itself is open-source and free, and is the foundation of many enterprise virtualization offerings, including those by Citrix, Virtual Iron, Amazon and IBM. While Xen and other hypervisors are available for free, Virtual Iron amongst other management tools are commercial products providing ways of making virtual machines easier to manage.

As a comparative exercise, Mark Adams of CLW demonstrated how open-source Xen can be used with a command-line interface. The Xen kernel is a modified Linux version, and can readily be managed by someone with Linux administration experience.

Xen instances running Windows 7
Windows 7 being migrated, while still running, between two Xen instances.

Mark ran a web service on a virtual machine on one computer, and then pulled the power cable on that set-up to demonstrate how the service migrated to a virtual machine on the second host, with no interruption in availability. He also demonstrated the live migration of the Windows 7 operating system.

The testing machines were built by Mark specifically for this session, using two Mini-ITX DG945FC boards with E6300 processors. This provided a small and cost-effective means to demonstrate automatic rollover between hosts. The set-up will be used in future for in-house testing of software, operating systems and virtualization.

CLW Testing Rig
Mark's testing rig

James Tansley of Hamiltons gave a brief overview of VMWare Infrastructure, which deploys across 3 servers. VMWare "VI" was recently instrumental in allowing him to integrate rapidly the networks of 3 large offices that were brought together on one site.


  • Lee Chisnall and Chris Williams, DNUK
  • James Tansley, Hamiltons
  • John Milsom, Fletcher Priest
  • Luke Ritchie, Dixon Jones
  • Ben Stratton-Woodward, Exposure
  • Bevan Badenhorst, Steffian
  • Jochen Glemser, David Chipperfield
  • Rory Campbell-Lange, Mark Adams and Tim Whiteley, Campbell-Lange Workshop

About the Forums

Campbell-Lange Workshop runs forums on a regular basis. Most are for IT managers, and are intended to provide an informal environment in which attendees can discuss ideas, approaches and ways to improve working practices while keeping abreast of changes in the industry.

Attendees of the February 2009 forum
Attendees of the February 2009 forum