Quoting IT Wire

The massive electricity requirements of data centres seems to be drawing a lot of attention lately. IBM is now promoting virtualisation as a means of cutting a data centre's energy consumption by reducing the number of servers.

AMD has just put out the results of a survey estimating the total annual electrical energy consumption of US data centres at 45 billion kilowatt hours.

You could roast an awful lot of pigs with that!

According to IBM, a single 19 inch server rack consumes electrical energy at a rate sufficient to roast a pig: 24 kilowatts. (IBM does not say how long the process would take so I am unable to extrapolate this to arrive at the total roast pig throughput capability of US data centres).

Not that IBM is suggesting you install a rotisserie above your servers: pig fat dripping through the vents would give you some nicely cooked chips but hardly edible.

No, IBM suggests you get rid of some of those servers by virtualisation. "Let's say you have three servers each running different applications or operating systems. If you can virtualise the work of two of them on the third so you can shut the two off, you've cut your server energy usage and heat generation by something approaching two-thirds," said Bernie Meyerson, IBM fellow, vice president of strategic alliances and chief technologist, systems and technology group."

Of course this assumes that your servers are not running full bore performing tasks more attuned to their design purpose than pig roasting. Meyerson argues that normally they have capacity to spare, but the difference in electrical energy consumption and heat output between a fully and lighted loaded server is minimal. "Servers use energy and give off heat whether or not they're in use 100 percent of the time or 15 percent of the time, but the actual difference in electrical consumption and heat generated isn't really that great between that 100 percent and 15 percent usage."

If you want to get technical about the pig roasting capabilities of data centres, there's a very learned looking paper on the IBM website: "Challenges of data center thermal management" Lots of mathematical formulae, but no recipes for roast pork.

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