Knotty problem

Shaun Fensom looks at the growing problem of data centre power consumption

Column for Ethical Consumer magazine Jul-Aug 2008

The word ‘net’ comes from the same root as ‘knot’. This says something about networks: the knots, or nodes, are just as important as the links between them. The Internet is a good example – the clever bits are in the nodes – servers and “routers” that store and direct data around the net. These computers are generally stacked 30 or 40 high in racks housed in “data centres”: secure buildings with “uninterruptable power supplies” which keep things running if the power fails. One data centre can cover many thousands of square feet and contain thousands of computers, all consuming power and generating heat. That heat is a problem. A rough rule of thumb says that for every watt of power consumed by the computers, another watt is needed to cool them down. A not-particularly-large data centre will consume over 5 MW of electrical power: in the ubiquitous “enough to power a town the size of” measure, that’s a town with a population of about 10,000. For much of the time the computers will be waiting in an “idle loop”, doing nothing but generating heat to keep the air-conditioning busy.

There is now a big drive to cut the energy consumption of data centres – partly because the costs of running them are so high, but also with a view to decreasing carbon emissions. We tend to expect the worst from the big corporations, but they are often in a better position to build properly planned and managed data centres. Some of the biggest in the industry now work together in an organisation called The Green Grid, which aims to develop and encourage best practice. BT for example claims to have cut data centre consumption by over 60% during the last decade using techniques such as fresh air cooling and “virtualisation” where tasks are shared between computers. Given that its centres still account for almost 0.7% of the UK’s power, that’s a big difference.

Coincidentally, the best estimate for the consumption of all the routers and servers that make up the Internet is about 0.7% of world electricity consumption. That’s already a lot. But with the number of computers connected to the net doubling every three years, we need the data centre operators to do a great deal more to increase efficiency.