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Jul. 7, 2010

IBM said this morning that it has successfully delivered a water-cooled supercomputer to the Zurich ETH university, saying it uses up to forty percent less energy than an air-cooled computer, and that it has a reduced carbon footprint because its waste heat is used to warm adjacent buildings to the university.

The "6T-Flop" experimental supercomputer is called Aquasar and has been designed and built by IBM researchers in Zurich.

The new mainframe was designed from a combination of Cell and Nehalem processors, and has a total of three chassis, two of which use an efficient water-cooling system.

Each chassis has 11 BladeCenter QS-222 IBM servers, each of which has two PowerXCell 8i processors, and three BladeCenter HS-22 servers, each of which has two Intel Nehalem EP CPUs.

IBM said it is water-cooling this supercomputer the same it has in the past for its venerable mainframes. However, intensive effort has been put into the design of the water-blocks to maximise the heat transfer from processors to the liquid coolant used in the machine.

Overall, water-cooling is a lot more efficient than air-cooling, and uses less energy based on IT equipment operating inside a cooled data centre.

IBM says Aquasar will help it build more energy-efficient supercomputers, and quotes Professor Dimos Poulikakos, the Thermodynamics laboratory head at ETH: "In the future it will be important to measure how efficiently a supercomputer is per watt of equivalent CO2 production."

Aquasar is said to have its carbon footprint reduced by up to 85 percent because its waste heat is used to warm adjacent buildings. But this has Aquasar's carbon footprint offset by the saved carbon that would have been used in heating the buildings, and Aquasar's waste heat is not much use in the summer.

The better direct measure is that the Aquasar installation uses up to 40 percent less energy than if it were air-cooled.

IBM engineers will monitor Aquasar's operation in ETH's Department of Mechanical and Process Engineering, comparing and contrasting the air-cooled and water-cooled chassis to further optimise the water-cooling system.

It may even be possible to over-clock supercomputer processors by using water-cooling to keep their temperature inside safe operating limits, and thus gain critical performance and energy consumption benefits in the future.

Also used in the Los Alamos Roadrunner system, IBM's PowerXCell 8is seems to be intended for the massive number-crunching involved in the complex applications that Aquasar is currently running.

Introduced in May 2008, the PowerXCell 8i is based on cell microprocessor technology developed by IBM, Sony and Toshiba. It is a high-performance, double-precision floating point product with a 65nm feature size.

The efficient water-cooled chassis feature water-blocks (cooling elements attached to the processors) which have water at 60 degrees C circulating through capillary tubes and picking up heat from the processors, rising to 65 degrees C and keeping the processors below their 85 degrees C upper limit.

The water then goes through a heat exchanger, goes back down to 60 degrees, passing nine kilowatts of thermal power into the ETH building heating system, and then returns back to the processors for another identical cooling cycle.

Source: IBM.

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