Linux based virtualisation – the way to save money and go green

David M Williams
Sunday, 13 July 2008 22:09

Business IT - Technology

Microsoft’s latest release of their server product, Windows Server 2008, promised something big: a built-in hypervisor. Yet, this did not ship with the product. In order to finally get out the door, Windows Server 2008 was released with only a beta version of this functionality. The release to manufacturing has only now not long taken place. There will be licensing costs if you want to use it, however. By contrast, Linux has had hypervisor technologies available already – and it doesn’t need it for best results, anyway.

Let me explain: as interest in virtual computers has grown the thought has arisen that maybe you can get rid of the operating system setup required in order to host and launch all these virtual environments. With a hypervisor the goal is to get as run the virtual computers as close to the bare computing metal as possible. The hypervisor is a small piece of software – far smaller than a traditional operating system installation – which controls the processor and the allocation of physical memory between virtual machines. It will keep the machines separate from each other.

There are several hypervisor-based software packages for Linux and one of the best known is Xen (now a Citrix product.) This is open source and comes in several versions, one of which is totally free for use. Nicely, the team behind Xen contribute back to Linux and have submitted kernel patches which have been included by Linux directly back into the Linux kernel.

The team behind Xen allege their virtualisation technology is widely acknowledged as the fastest and most secure of its genre. It is a mature and stable product, and is far from being just out of beta.
There are other moves afoot within the Linux world to actually negate the need for a hypervisor at all. Many of the facilities the hypervisor provides – like preventing different virtual machines from interfering with each other’s memory – are all things which Linux caters for out of the box. The approach is thus being considered to build virtualisation support directly into the Linux kernel. If this were done it would suddenly be available for any Linux distro worldwide.

The idea here is that a tiny – but standard – Linux installation would then be fully able to launch and manage a plethora of virtual computers. There would be no need for a full blown operating system installation on the computer just so it can run virtual machines. This has potential to go much further.

While Windows is proprietary and licensed for a fee Linux can be freely used. It will be possible in time for server computers to actually come with the Linux kernel embedded on their chips. At this time virtualisation will have reached dizzying new heights. No longer will a computer be thought of as devoting itself to a single purpose, but instead can be running an entire farmyard of differing platforms, environments and applications. And with Linux the software overheads are drastically reduced, from already existing hypervisor based systems through to the inevitable Linux kernel embedded into the computers of tomorrow.