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August 28, 2009 • Vol.31 Issue 22
Page(s) 22 in print issue |
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Affordable Cooling Strategies
Boosting Cooling Efficiency Doesn’t Always Mean Breaking A Data Center Budget
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Key Points
• Methods for boosting cooling efficiency, such as blocking cutout holes and using blanking panels, need not cost much, if anything at all.
• Employ a hot aisle/cold aisle approach to maximize the cooling efficiency in server rows and consider using plastic curtains to optimize the approach.
• Battle heat with heat—test to determine the safe limits of hardware and increase the temperature in the data center accordingly to save on cooling costs.
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Heat is a tough customer. Failing economy? Too bad. Lost some customers? Too bad. Layoffs? Too bad. Regardless of business challenges, heat rarely grants any leeway to data centers. Yet with some determination and old-fashioned know-how, it’s entirely possible to one-up heat without further dwindling your budget.
 “Implementation and diligent enforcement of relatively simple concepts such as aisle containment and optimization of current cooling systems allow data centers to support higher densities without necessarily upgrading the cooling systems. [Companies can] make the appropriate improvements to efficiency in-house using many materials that can often be found in a data center environment or a home improvement store,” explains Josh Sayers, operations engineer for Latisys (www.latisys.com).
 Benefit Through Blanking
Although vendors may try to convince otherwise, addressing heat problems doesn’t always require a huge capital outlay—if any money at all. Chris Loeffler, global applications manager for Eaton Data Center Solutions (877/785-4994; www.eaton.com/powerquality), says that one of the least expensive methods for improving cooling efficiency is blocking any cable cutout holes or openings in a raised floor that weren’t originally designed for the floor. Data center personnel can also apply this philosophy to server cabinets.
“The quickest and potentially cheapest way to improve cooling is to install blanking material in cabinets to block any empty U space on the front side of the cabinet,” Sayers says. “With no budget, you’ll need to be creative. For example, if you can’t purchase commercially produced blanking panels, look around. There are typically plenty of server boxes that make great blocking material in a pinch.”
Loeffler also recommends identifying “orphaned” equipment, such as servers and other IT gear, that aren’t currently in use and uninstalling them if possible or at least shutting them off. Further, check all servers to ensure that any built-in power-saving functions are in use. According to Loeffler, many older servers have power-saving features, but they may have been shipped with the features turned off.
A Scientific Approach
Data centers can also employ the use of software to control power consumption and cooling based on the heat profiles of different processors. For example, Partha Ranganthan, distinguished technologist at HP Labs (www.hpl.hp.com), recommends using software to direct different computing tasks to processors based on the current temperatures and the amount of expected heat that will be created.
“In other words, processors would be turned on and off or given smaller or bigger amounts of work to do based on policies that balance power and cooling resources and needs. Similarly, servers—both virtual and real—could be assigned work based on sensing the temperature around them and could use thermo-fluids policies to achieve a balance of power and cooling. This would result in the data center cooling resources operating at an efficient operating point,” Ranganthan says.
Ranganthan also suggests that IT managers consider combining sensors with control nodes that adjust the distribution of cooling resources according to the needs of the IT equipment. Using this strategy, data centers can optimize cooling by focusing on areas that truly need to be cooled. Ranganthan says that by using a similar technique, HP Labs has reduced the power required to cool data centers by 30 to 60%, depending on facility infrastructure.
It’s Curtains For Heat
One of the most common methods for boosting cooling efficiency without adding expensive hardware or infrastructure is the use of a hot aisle/cold aisle approach. Although cabinet manufacturers are increasingly building cold- or hot-air containment systems that have walls between the cold air intake side and the hot air output side of IT equipment, Loeffler points to a less expensive method used by the food and shipping industries.
“Flexible plastic curtains are placed above the racks or on the end of the rows, from the top of the rack—or floor—all the way to the ceiling, separating the hot and cold air. One thing that does need consideration with this is that you don’t disable parts of your fire suppression system by adding in the curtains. So make sure your plan includes updating the fire system to meet code requirements, as well,” Loeffler advises.
Embrace Warmth (To An Extent)
Data centers struggle daily with the battle against heat, but for some, that battle might be in vain. According to Harry Schechter, founder and CEO of Temperature@lert (866/524-3540; www.temperaturealert.com), you can cut back on cooling costs by simply raising the temperature in your data center. In fact, for every degree higher, you’ll realize about 4% savings on your energy bill. Loeffler agrees, adding that many sites are overcooled because they keep racks at 65 degrees Fahrenheit, for example, when servers might be fine at 75 F.
To properly gauge the safe limits of hardware, Loeffler suggests conducting temperature monitoring and failed unit testing. “Test if you still have full cooling capacity even if you lose a cooling unit. If so, and you have no issues with hot spots, raise the room temperature to something inside the ASHRAE limits, which are being raised higher. In addition to added cooling capacity, you will not have to do so much humidification because you won’t be drying the air so much,” he says. 
by Christian Perry
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