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The cost of keeping cool

Data centres focus on improving the efficiency of IT equipment. But it is equally important to look at the bigger picture and assess the cost of cooling requirements, says Rajiv Sivaraman

| | Jun 30, 2011 | 3:54 am
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Data centres focus on improving the efficiency of IT equipment. But it is equally important to look at the bigger picture and assess the cost of cooling requirements, says Rajiv Sivaraman. He argues that energy benchmarking is the key to improving energy performance.

Electricity has always been a significant overhead in an environment where data processing, data transmission and data storage are the primary functions. However, typically, Total Cost of Ownership (TCO) models in data centres have tended to focus on driving down the cost of the IT equipment rather than seeking to optimise the energy expended in keeping it cool. This is, perhaps, understandable when energy costs are low. However, at a time when they are not only at an all-time high but also expected to double in the next 10 years, a rethink in strategy which recognises the role of energy is certainly advisable. Critical to this is managing the cooling requirements, given that an estimated 40% of a data centre’s overall power is used for this purpose.


A simplistic approach to the energy equation, perhaps, suggests that it should not be the focus for data centres. This is especially so, if we take into consideration the fact that, on an average, the performance per watt of a server doubles every two years, resulting in a constantly reduced cost per performance and constantly higher performance per unit. However, this is certainly far from the complete picture. Power capacity is increasing exponentially – almost doubling since the year 2000 – as data centres scale their infrastructure to keep pace with the demand for processing and delivering increasing quantities of video, voice and data through a vast global network of several billion devices. Business needs to continue to outstrip improvements in server performance. This implies that every year, the number of server units is growing. The increased density of the servers brings with it challenges in terms of accumulated heat load ‘hotspots’. And, as business operations become ever more reliant on data centres for business continuity, so does the need increase for more expensive designs, which try, as far as is possible, to prevent any interruption to the IT network. Energy costs are, therefore, increasingly becoming the focus, as data centres seek a more transparent approach to metering, monitoring and controlling their energy use.


It might appear to be a fairly obvious point, but nonetheless one worth making, that in order to understand its energy consumption and how it can be optimised, a data centre needs to have a means of measuring it. Many data centres actually run at temperatures significantly lower than that required by the IT equipment. Recognising this fact can be a very useful starting point for cutting energy and its attendant cost. Energy benchmarking is the key to improving energy performance, which will provide a top level indicator of potential savings. It establishes a baseline for energy use in a typical facility, provides comparisons against similar facilities, identifies operational or maintenance problems, highlights areas for potential improvement and establishes best practice for incorporating into future designs.

In the light of the benefits listed, it is evident that monitoring and control systems need to be put in place to keep track of how and where energy is used within a data centre. Such systems are designed to provide integrated metering and monitoring to detect and respond to a variety of events that can not only assist in reducing energy consumption but also help warn of situations that actually threaten the operation of the data centre.


As already indicated, high quality and reliable cooling systems are, or need to be important features of any data centre, as they help avoid hardware malfunction and, thus, maintain the all-important continuity of service on which a centre’s clients rely. Therefore, if an effective cooling management strategy is not employed, the air-flow will be dictated by a data centre’s physical layout and the characteristics and positioning of its IT and cooling equipment.

It is important to note that the means to prevent hot air and cold air mixing, often referred to as Hot/Cold Aisle design, is a fundamental goal in a data centre’s cooling technology. This involves the effective management and control of air-flow to help prevent short-circuiting of cooling systems, isolating the hot exhaust air from the cool air supply, and thereby lowering the load of the cooling unit and maximising efficiency.

In fact, the simple act of ensuring that cooling units are moved closer to IT equipment can reduce cooling costs by more than 30%, compared with traditional approaches to cooling. The use of filler insulation panels within racks to isolate the hot air from the cold air can also reduce wasted energy in closed rack cooling, while independent cooling units can be used for equipment in different function rooms to ensure that cooling capacity is distributed on an ‘as-required’ basis, again reducing unnecessary power consumption. Also, ‘free cooling’ technology can be employed using filtered external fresh air, with the added benefit of creating a positive air pressure to effectively block dirt from outside, ensuring a clean environment.


While cooling is a very important factor, integrated systems not only monitor cooling efficiency but also take into account many other features which can impact the overall energy use.

Central to the Active Energy Management approach is the need for transparency in power flows. Current consumption and power flows need to be analysed through power monitoring devices, E-counters and communication-capable circuit-breakers. Through communication interfaces, these devices can be integrated into high-level building automation and energy management systems that consider energy efficiency in a much more holistic way, providing monitoring and control through the integration of all data from the building control, fire safety, security, lighting and power systems. Energy reports can be generated by these building automation and control systems, with the data retrieved from the process units which record the values delivered by the system’s field devices. Trends can be established from a number of different reports, including energy consumption, energy costs, CO2 emissions and comfort requirements.


There has undoubtedly been a shift in terms of the TCO in data centres. No longer is it the cost of the IT equipment that represents the largest element, but rather, the means through which the equipment is powered and cooled. With energy costs only set to rise, and the seemingly insatiable demand for more and more business applications requiring increased capacity from data centres, the spotlight on energy costs will become even greater.

The writer is Senior Vice President, Head, Market Development Board Data Centres, Siemens Building Technologies Division. He has spent over 18 years in the field of industry, infrastructure and energy sectors with specialisation in project management, marketing and new business/market initiatives

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