Server virtualisation has been changing the way companies buy, deploy and manage servers. They've done this by reducing the number of physical servers in an IT environment and consolidating servers, saving space, reducing power and the time taken to install a server. VMware and Microsoft still dominate this market but recent developments by XenSource make their range of virtualisation products appealing.
The family of XenSource products stem from Xen, which is a free virtualisation platform distributed under the GPL licence. XenSource however offers its own enhancements by improving the performance and management. XenSource offer three choices: XenEnterprise, XenServer and XenExpress. Xen Enterprise is aimed at high density server consolidation for the most demanding environments. XenServer consolidates up to eight virtual servers and XenExpress is the entry level option which can consolidate up to four virtual servers on one system.
We were shipped XenServer, and found it had an installation that differs dramatically from VMware or Microsoft's solutions. The host component of XenServer needs to be installed on a bare system as it doesn't run as a standard application on top of an existing operating system. Then Xen Hypervisor is allowed to runs natively which XenSource claim should provide improved performance than if it was running on an existing hosted operating system.
The actual installation is pretty straightforward and if you know Linux you will be familiar with the set-up processes. The installation installs the Debian distribution, its driver support and also installs Xen Hypervisor. You also may want to use a powerful server as your host since this machine will run all your virtual machines.
You must remember to use at least 1GB of RAM. We tried to test the XenServer with less than 1GB of RAM and we had problems starting XenServer. Initially we thought these errors were brought upon by something else but soon realised that by installing 1GB of RAM on the host machine we were able to successfully start XenServer.
The second part of the installation is to install the management software. This needs to reside on a different machine to the host running XenServer, but doesn't need to be installed on anything with a lot of processing power. Then, using the management software you can connect to the XenServer in order to manage your virtual machines. You can start and stop the machines and also monitor the CPU usage, free memory, and disk and network rates.
The latest release of XenServer contains a number of new features where Xen VMs can run Windows 2000 Server as well as Windows 2003 Server and Windows XP2 with support for multiple CPUs. Basic support for iSCSI is also included. XenServer also has an option which converts existing physical installations into virtual machines.
XenServer still has a fair way to go in order to catch up to the current functionality already offered in VMware and Microsoft's virtualisation solutions -- but it's quickly improving and is a lot more affordable.