Data Center Density Hits the Wall

Why the era of packing more servers into the same space may have to end.

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Once Microsoft began charging for power, its users' focus changed from getting the most processing power in the smallest possible space to getting the most performance per watt. That may or may not lead to higher-density choices -- it depends on the overall energy efficiency of the proposed solutions. On the other hand, Belady says, "if you're charging for space, the motivation is 100% about density."

Today, vendors design for the highest density, and users are often willing to pay more for a higher-density server infrastructure to save on floor space charges, even when performance per watt is lower because of added power distribution and cooling needs. But on the back end, 80% of operating costs scale with electricity use -- and the electromechanical infrastructure needed to deliver power and cool the equipment.

Belady, who previously worked on server designs as a distinguished engineer at HP, argues that IT equipment should be designed to work reliably at higher operating temperatures. Current equipment is designed to operate at a maximum temperature of 81 degrees. That's up from 2004, when the official specification, set by the ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) Technical Committee 9.9, was 72 degrees.

But Belady says running data center gear even hotter than 81 degrees could result in enormous efficiency gains.

"Once you start going to higher temperatures, you open up new opportunities to use outside air and you can eliminate a lot of the chillers, but you can't go as dense," he says. Data centers in some parts of the country already turn off chillers in the winter and use economizers, which use outside air and air-to-air or air-to-water heat exchangers to provide "free cooling."

If IT equipment could operate at 95 degrees, most data centers in the U.S. could be cooled with air-side economizers almost year-round, Belady argues. And, he adds, "if I could operate at 120 degrees, I could run anywhere in the world with no air conditioning requirements. That would completely change the game." Unfortunately, there are a few roadblocks to getting there.)

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