Supercomputer techies just want to chill

The builders of tomorrow's supercomputers will have to find new ways to cool their systems.

'This is a very serious problem,' said Srinidhi Varadarajan, architect of the Terascale Computing Facility at Virginia Polytechnic Institute and State University, in Blacksburg, Va. 'Today's processors produce a phenomenal amount of heat.'

One rack of servers can easily be cooled by an air conditioner, but 'when you have a hundred racks, that is not viable,' Varadarajan said at the recent National High Performance Computing and Communications Conference in Newport, R.I.

SGI chief technology officer Eng Lim Goh said supercomputers continue to make giant leaps in processing power, but cooling technologies are not advancing as rapidly. As a result, system designers see a growing disparity between the amount of heat generated by newer supercomputers and data centers' ability to keep cool.

Newer supercomputer facilities 'feel like wind tunnels,' Goh said. 'People are starting to think about a different medium. Air can only carry so much heat.'

Virginia Tech chose a hybrid liquid-air cooling system because the traditional cooling approach would be inadequate due to the data center's restricted space.

Varadarajan estimated that the 1,100 Apple G5s in the system produce 3.2 million British thermal units of heat in a 3,000-square-foot space.

The usual approach would have forced air up through the perforated floor tiles with multiple fans, Varadarajan said. The computers would suck in the cooler air and blow out the hot air, which ceiling exhaust fans would carry away.

But Varadarajan's team calculated the air would have to blow through the facility at 60 mph to adequately cool the G5s.

So Virginia Tech picked a hybrid liquid-air setup: Chilled liquid travels through pipes under the facility's raised floor. Fans blow cooled air off the pipes, which carry 750 gallons of liquid per minute.

Besides reducing wind, the hybrid system is also less expensive, Varadarajan said. An all-air cooling system would have cost around $5 million to build, far too pricey for the university. The hybrid system cost less than $1 million.

About the Author

Joab Jackson is the senior technology editor for Government Computer News.

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