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Energy Guru

IBM cooling expert Roger Schmidt says the positioning of machines

Modern data centers generally adhere to cold aisle/hot aisle. But in many ’90s-era data centers—which were built and populated when computing power and energy costs were a fraction of what they are now—machines may all face one way, or every which way.

“If every row is arranged in the same direction, with exhaust air coming out the back of one row and then blowing onto the front of the next, the temperature will increase on each row,” Schmidt says. “It doesn’t work.”

Not everyone who knows about cold aisle/hot aisle feels comfortable implementing it. Schmidt was recently in South Africa meeting with a large customer. “It was a mess, and they knew it,” he said. “But if it’s not set up that way, shutting everything down and re-cabling all the machines can be a major problem. It’s hard to switch over.”

On the other hand, some customers fail to recognize that data centers should be cooled, as opposed to cold. “Even if people do have cold aisle/hot aisle set up, walking through that cold aisle can feel like a meat locker,” Schmidt says. “A higher temperate, up to 80.6 degrees on the cold aisle, is allowable and encouraged for clients to save energy.”

Neil Tardy is a contributing writer to IBM Systems Magazine. Neil can be reached at



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