Early customers for the service include the DreamWorks digital animation studio and Pacific Northwest National Laboratory, which is building a mammoth supercomputer with hundreds of two-processor Itanium servers from HP. The laboratory is likely to use the dynamic cooling technology, Donabedian said. Forcing the issue
In their earlier days, computers had relatively few processors -- the hottest part of a machine -- in a large cabinet. But new server models are forcing the cooling issue, said Illuminata's Freund. Rack-mounted and "blade" server models currently fit dozens, or hundreds, of processors in a six-foot rack. In addition, high-end multiprocessor servers from Sun Microsystems already have begun topping the 100-processor mark in a single chassis. Compounding the issues posed by hotter machines is the technology that makes centralised computing more popular. For example, most higher-end Unix servers today can be divided into multiple "partitions", each with its own copy of the operating system. That feature makes it easier to replace numerous widely dispersed low-end servers with a single easy-to-manage large server, a trend called "server consolidation." At the same time, special-purpose storage area networks (SANs) let administrators more easily use large, centralised storage systems instead of smaller ones attached to each server. Rival manufacturers -- and their customers -- are increasingly looking at the overall cost of running systems, taking into account, for example, electricity charges as well as computer price tags, said Charles King of the Sageza Group analyst firm. "To save money over time, you need to start looking at cooling costs, the cost of doing wiring maintenance, the cost of bringing a server online," King said. "IBM in particular has been really aggressive in the holistic view of the datacentre." The liquid cooling solution
In the long run, adjusting air flow will only help so much with cooling datacentres, and more radical changes will be required. The top contender is cooling with water, or some other liquid that's more efficient than air at absorbing heat from processors. This means liquid-cooled systems, such as older IBM mainframes and Cray supercomputers, could experience a renaissance. IBM researchers working on a super-dense storage system called Collective Intelligent Bricks have begun advocating a return to liquid cooling. "We are getting actually feedback from high-end customers who say -- about water cooling -- 'What took you so long to get back to it?'" said IBM researcher Winfried Wilcke in an email interview. While IBM favours centralised water-cooling systems, HP's Donabedian believes smaller, more local cooling also is feasible. It's possible to liquid-cool individual processors or to spray processors with special fluids that can be collected after they cool a chip, then recycled. "Probably within about five years you'll really begin to see liquid cooling hitting the market," Donabedian said. "All the computer manufacturers are going through their gyrations now, experimenting and trying to figure out the best way to go."