March 2, 2006 4:00 AM PST
Is DC the power to solve heat problems?
- Related Stories
Turning nature's design into scientific breakthroughMarch 1, 2006
Electric slide for tech industry?February 1, 2006
Sun gives Niagara official nameNovember 13, 2005
IBM brings Power blades to telcosJune 7, 2005
Intel to throttle power by enhancing siliconAugust 29, 2004
(continued from previous page)
Several power and cooling problems now afflict those who run data centers--large rooms filled with the computing, networking and storage equipment at the heart of large-scale information technology operations.
Processors throw off vastly more waste heat than before, a situation aggravated by the way they're packed in more densely. On top of that, the appetite for equipment shows no signs of abating, as computerization penetrates ever more deeply into people's lives. The problem has become severe enough that installing computers now often requires discussions not just with IT staff but also with those in charge of the power and air conditioning for a building.
"There's a merge coming between IT and facilities. You can't just talk to the IT guy. You have to talk to facilities as well," said Ron Mann, director of engineering in HP's Infrastructure Group.
Historically, a standard 6-foot-tall rack of computing gear consumed 2 to 4 kilowatts of power and threw off a corresponding amount of waste heat, Mann said. Today, 7 to 10 kilowatts is more common, and 15 to 30 kilowatts can be found. For perspective, 15 kilowatts is the same amount of power used by 150 100-watt light bulbs.
Using DC doesn't help the problem of hot, power-hungry processors, but it does get rid of power supplies and their cooling fans in a server. They don't go away entirely, of course, but typically are relocated at the top of a rack where their hot waste heat will rise and not be drawn into server cooling intakes.
Although HP isn't as aggressive a DC advocate as Rackable, it does use the approach to power its blade servers, using bulk power supplies within a rack. Putting a larger power supplies inside the rack is more efficient than having smaller ones in each server, Mann said. For example, four 5.25-inch-thick power supply units can power 96 blade servers with dual Opteron processors from Advanced Micro Devices, he said.
Sun's Bechtolsheim is unconvinced of the merits of DC, though. The crux of his argument is that DC requires two conversions: one from outside AC to 48-volt DC for distribution within the building, and a second, within servers, from 48 volts to 12 volts. Even if each conversion is 90 percent efficient, wasting 10 percent of power as heat, the combination makes the overall process 81 percent efficient.
By contrast, a single AC-DC conversion with the server uses power supplies rated at 90 percent efficiency, Bechtolsheim said.
Tim Dougherty, director of blade strategy at IBM, doesn't always agree with Sun, but this time is an exception.
"It's one of those things that always looks better on paper than it turns out to be," he said. Sure, there are DC advocates, but they can't sidestep power conversion problems altogether, he said: "All they do is move the problem somewhere else in your computer room."
36 commentsJoin the conversation! Add your comment