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HPC 2013-14 | Energy efficiency


Power versus performance


Energy efficiency remains one of the most critical issues in HPC. Beth Harlen investigates the approaches being taken to tackle this challenge


Enter into any conversation about pushing the boundaries of high-performance computing and one topic is certain to come to the forefront of discussions: power consumption. For some time the industry has been driven towards improving the performance of systems, but with less regard being paid to their energy efficiency. Now, rising power bills and the estimation


that, if we continue along current technology lines, exascale systems will consume hundreds of megawatts of power, have led to the understanding that power and performance must go hand in hand. Tere are a number of ways in which we can tackle this challenge – namely: cooling technologies; advances in hardware; and the energy efficiency of the applications that run on it. In the words of Geoff Lyon, CEO and


CTO of CoolIT Systems, cooling is the ‘lowest-hanging fruit’ for addressing power consumption. It’s easy to understand why when you consider the fact that the cooling portion of the energy consumption in a typical data centre can be responsible for up to 40 per cent of that centre’s total energy bill. Tat’s a staggering figure, but liquid cooling – especially direct contact – is improving that ratio through its ability to maintain cool, safe CPU temperatures without the need for power- hungry computer room air conditioners. Tere are data centre operators who will


have an aversion to the thought of liquid running through their racks – and, as Lyon points out, if they can manage to keep their data centre capacity in check with traditional methods such as air cooling, the impetus to explore alternatives is somewhat lessened. However, should temperatures rise – even by just a degree at a time – these operators


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could end up in the precarious situation where current methods are no longer capable of sustaining capacity. ‘Power density is a very important element


of any strategy to ensure that we continue to satisfy not only today’s data needs, but for years to come as well,’ said Lyon. ‘Liquid cooling is a fundamental part of


this equation – and, based on the maturity of the suppliers and systems available, the reliability of this method is getting to the level where people are becoming comfortable with the idea.’


Keeping cool Necessity is oſten cited as the mother of invention, and Lyon believes that sheer necessity will drive the industry to liquid cooling: ‘When anyone designs or provisions a data centre, it’s likely they will attempt to take the most conservative approach possible. Tis is all well and good, but we’re now at the stage where this simply won’t be enough to meet requirements over the next few years.’ According to Lyon, with direct contact liquid cooling it’s possible to support upwards of 40 or even 50kW per rack, with


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