The background on Apple’s ’103-degree data centre’

Patrick Thibodeau
28 April, 2014
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Apple is using solar arrays, including a 100-acre solar energy farm in Maiden, North Carolina, to help power a data centre there.

Apple allowed NBC’s Today show inside the facility last week and, during the tour, a reporter asked what the temperature was there. “It’s about 103 degrees in here,” said Lisa Jackson, Apple’s vice president of environmental initiatives and a former Obama administration EPA chief.

What wasn’t explained is that Jackson and the reporter were walking down a hot aisle, and feeling the fan exhaust. The experience may have been different if they had walked down the cold aisle, where the rack fronts face the aisle.

Apple isn’t disclosing details about its Maiden data centre operations, except at the 9144-metre (30,000-foot) level, so it’s unknown exactly what temperatures it’s operating at.

But it is possible to estimate a range.

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) sets temperatures and humidity guidelines for data centres based on what it knows about the equipment inside them. It recommends that data centres operate between 64.4 and 80.6 degrees Fahrenheit.

The recommended limit concerns the air intake temperature. The exhaust temperatures will be higher; how much higher will depend on the density and the quality of the air management, according to the Uptime Institute vice president Keith Klesner. But the temperature could be approximately 15 to 30 degrees Fahrenheit higher, he said in an email.

Dave Kelley, director of application engineering at Emerson Network Power’s Liebert Precision Cooling, narrowed it down further. “[Typically] if you have 80 degrees Fahrenheit entering the IT equipment in the cold aisle, you will have 100 to 105 degrees Fahrenheit leaving in the hot aisle,” he said. “All of these values are functions of how much work the IT equipment is doing. If it is not at full output, then the leaving temperature could be less.”

The points made by Klesner and Kelley, coupled with the 103 degrees cited by Jackson, suggest that Apple is running near or at the recommended ASHRAE temperature limit. To do so lets Apple save the most money on energy cost.

That strategy puts Apple in the forefront of data centre operators in terms of temperature limits.

According to Uptime, while cutting edge-type data centres are pushing the thermal envelope, most data centre managers are more conservative. A recent Uptime survey found that nearly half of all data centres reported operating at 71 to 75 degrees Fahrenheit. The next largest temperature segment, from 65 to 70 degrees, was 37 percent, it reported.

Data centre managers may err on the side of caution, because higher data centre temperatures can increase risk of equipment failure, but also require sophisticated controls to avoid hot spots and other cooling problems.

ASHRAE also sets ‘allowable’ temperature guidelines that go well above the recommended limits. Manufacturers can make equipment that can work at higher temperature ranges, all the way up to 113 degrees for equipment in the A4 class.

There are classes of equipment from A1 to A4, which represents the higher end of tolerance.

“Most operators will not operate to the allowable limit of the equipment, but rather some temperature below that. In A4 class equipment, maybe they will select 105 degrees Fahrenheit,” according to Don Beaty, a consulting engineer and publications chair of the society’s Technical Committee 9.9 for mission-critical facilities, technology spaces and electronic equipment.

by Patrick Thibodeau, Computerworld

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