news
Technology | DOI: 10.1145/2347736.2347742
Gregory Mone
Redesigning
the Data Center
Faced with rising electricity costs, leading companies
have begun revolutionizing the way data centers work,
from the hardware to the buildings themselves.

LAte lAst YeAr, Stanford Uni- versity researcher Jonathan Koomey released a report de- tailing a few surprising trends about the energy squanderers known as data centers. Previous estimates suggested that electricity consumption in massive server farms would double between 2005 and 2010. Instead, the number rose by 56% worldwide, and merely 36% in the U.S. The slower-than-expected growth stemmed from a number of changes, including a stagnant economy and the rise of virtualization software.

Yet experts say a more fundamental change is also starting to take effect— one that could lead to much greater improvements in efficiency. Over the past seven or so years, leading companies have begun revising the way they design, maintain, and monitor data centers, from the physical building all the way down to the hardware doing the computation. Recently, Google, Facebook, and other major companies have begun releasing details on the efficiency of their facilities, and revealing a few of the technological tricks they have devised to achieve those gains.

Still, these leaders are the exception rather than the rule. There are no solid estimates of the total number of data centers in the U.S., and the Silicon Valley giants are secretive about exactly how many they operate, but they hardly dominate from an energy standpoint. In all, U.S. facilities consume between 65 and 88 billion kilowatt hours per year, and Google, for instance, accounts for less than 1% of that figure.

The fact remains that the average data center is still largely inefficient. The standard measure of a data center’s efficiency is its PUE, or power usage effectiveness. PUE is the total

over the past seven
or so years, leading
companies have
begun revising the
way they design,
maintain, and monitor
data centers, from
the physical building
all the way down to
the hardware doing
the computation.

energy used to operate a data center divided by the amount devoted to actual computing. That total includes lighting, fans, air conditioners, and even electrical losses as power is transferred from the grid to physical hardware. Ideally, a data center would run at a PUE of 1.0, and all of the electricity would go toward computing. Yahoo!, Facebook, and Google have all touted facilities scoring below 1. 1. Across industries, though, these numbers are hardly common. “What happens in the typical data center is that it’s more like 2.0,” explains Koomey.

Until recently, most companies did
not even bother measuring PUE. They
had little sense of how and where en-
ergy was used or lost within the facility.
“The primary reason all of this happens
is because there’s not great accounting
of the energy in data centers,” says Raju
Pandey, the chief technical officer of
Synapsense, a Folsom, CA-based com-
pany that performs data center optimi-
zations. “There’s an incredible amount
of wastage.”

heating up

If you had walked into the average data center 10 years ago, you would have needed a sweater. The American Society of Heating, Refrigerating and Air-Conditioning Engineers recommended these facilities be maintained at temperatures between 60 and 65 degrees Fahrenheit to prevent the equipment inside from overheating. And the machines that cool the space are often inefficient. “Traditional data centers basically have the same air-conditioning unit you’d put in your house,” says Bill Weihl, Facebook’s manager of energy efficiency and sustainability.

The rationale was that warmer
temperatures could lead to hardware
failures, but several experts doubt-
ed this was actually the case. When
Google began planning a new breed
of data center in 2004, the company
started testing the temperature lim-
its of its hardware. “We started run-
ning our servers warmer and moni-
toring the failure rates,” says Joe
Kava, Google’s director of data center
operations. In the end, Google simply
did not see any major problems. “The
servers ran just fine,” he adds, “and if
you know your servers can run at 80
degrees, you can redesign your cool-
ing system entirely.”
Google found that it could avoid re-
lying on giant air-conditioning units,
as did other companies. The most ef-
ficient data centers now hover at tem-
peratures closer to 80 degrees Fahr-
enheit, and instead of sweaters, the
technicians walk around in shorts.
Facebook’s data centers in Lulea, Swe-
den and Prineville, OR, have no me-