A guide to server efficiency

Alan Stevens ZDNet.co.uk

Published: 05 Jun 2007

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The virtualisation story
We’ve left virtualisation until almost last, not because it’s unimportant — far from it — but to allow space to do justice to this highly influential technology. And it really is worth it, virtualisation being one of the best ways to really ramp up server efficiency.

That’s because by virtualising the processors, memory and other hardware resources you’re able to configure and run multiple virtual machines (VMs) on the same physical server platform. Each of these VMs can then run an independent guest operating system, with the virtualisation software sharing out access to physical resources so that they’re effectively utilised rather than sitting idle while still consuming power and generating heat. If you beef up your hardware using the latest 64-bit multi-core processors, server consolidation takes on a whole new meaning.

Virtualisation also helps to address issues with older single-threaded applications as otherwise unemployed processors or processor cores can still be used by other VMs. Plus it’s possible to take advantage of the latest 64-bit processor technologies even when still running predominantly 32-bit applications and operating systems.

There are several different types of virtualisation, but in the industry-standard server market two approaches predominate. The first is where virtual machines running guest operating systems share access to server hardware via a host operating system — typically either Windows or Linux — through a virtual machine monitor (VMM), which is run much like any other application. Examples of this include VMWare Server from market leader VMWare, and Microsoft’s Virtual Server 2005, both of which can be downloaded for free and used to host both Windows and Linux VMs.

VMware is the market leader in virtualisation technology.

The other approach involves the use of a virtualisation 'hypervisor', which does away with the host operating system. Because it doesn’t use any host OS services, the hypervisor can be better tuned to the virtualisation role and, in theory, should enable guest VMs to make more efficient use of the host hardware resources.

Again, the market leader here is VMWare with its ESX Server product, now part of its Virtual Infrastructure 3 (Vi3) solution. This can be used to host a variety of guest VMs running Windows, Linux and Solaris with dynamic load balancing of resources to make the most efficient use of the supporting hardware, plus live migration of virtual machines for failover and maintenance.

Microsoft is also planning a hypervisor solution that will form part of Windows Server 2008 (it will be called Windows Server Virtualisation), although this won’t ship until up to 180 days after the new server OS is released. It will also lack the load balancing and live migration facilities that were originally planned, which will now appear in a later release.

XenSource is another increasingly popular virtualisation vendor, with its open-source Xen products. The processor vendors have been doing their bit too, adding hardware support for virtualisation to their latest chips. To this end you should look for processors with either Intel-VT or AMD-V capabilities. However, note that while some virtualisation solutions are reliant on these processor extensions, others can get by without them, with no real impact on overall effectiveness.

A holistic view
There are many other areas to examine if you want to improve server efficiency. Do you really need all those redundant power supplies, for instance? Similarly, you might want to look at reducing the number of internal disks dedicated to each machine. Direct-attached storage is both inefficient and hard to manage, whereas a SAN (Storage Area Network) can drastically cut the number of drives you have spinning away, as well as making it a lot easier to expand, protect and generally manage your storage requirements.

Operating systems can also have a bearing, as can applications — especially older programs which, if re-engineered using new technologies, can be made to do a lot more on fewer, less-powerful, servers. Indeed, if efficiency really is important to you, it’s worthwhile taking a much more holistic view of your servers and everything to do with them. Consider everything from the processor up, and you may be surprised at the savings you can make.

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