Do SuperComputers Turn a Green Data Center Gray? By Doug Maloney

Views and Opinions on Green IT (Dec 11 2009) Power and Cooling , Carbon Footprint , Supercomputer

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   Green data center technology and supercomputing aren't two things that go well together, and there's a reason why.  Faster computational performance in a densely packed space requires the hottest – literally – CPUs available packed very close together.  All that heat requires somewhere to go, which requires cooling and more dollars to the power bill.

    Exhibit A for this is IBM's Blue Waters supercomputer being built at the University of Illinois Urbana-Champaign campus, as reported by News.com.  The machine is getting its own 88,000 square foot building and be theoretically capable of speeds of 10 petaflops, about 10 times as fast as the fastest supercomputer today.

    Blue Waters will use lots and lots of brand new IBM Power7 processors expected out in the first half of 2010 – a total of 16,384 chips together.  Each Power7 processor integrates eight processing cores in one chip package and each core can in turn execute four tasks, so net-net each chip can perform 32 separate operations at once.  The chip will clock between 3 to 4 GHz, lower than the Power6 family's 5GHz operational speeds because otherwise the chip would "melt."

    Compounding matters is that all the chips have to be close together to transfer data between them at peak speeds of up to 192GB per second.  Speaking apart the chips might make sense from a cooling perspective, but having to travel farther means more wire and slower transfer rates.

   Needless to say, cooling all these densely packed chips is a big issue.  Water cooling will be incorporated into the racks of the machine because the processors will be water-cooled directly to pull the heat out.  Using water is being touted as being "more efficient" with the water being run through an on-site tower for chilling water.  Energy consumption is expected to go down in the winter months since the cold Illinois winters will provide a more efficient heat sink.

   Ironically, there's a list for "green" supercomputers, the Green 500, www.green500.org. Published by Virginia Tech, the list provides a ranking of the most energy-efficient supercomputers in the world and the latest report notes that even supercomputers are starting to get more energy efficient.   

   There's something a little disturbing about putting the fastest supercomputer in the world – a Cray X5-HE operated by Oak Ridge National Laboratory – as the 44^th most "Green" when it consumes 6950.6 kilowatts in operation.  Certainly the device delivers 253.07 MFLOPS/Watt, but no matter how you slice it, turning it on and keeping it running on a 24 x 7 x 365 basis isn't exactly what the greenest activity around.

   
   

   
   

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