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16 16 P P a r t I : a r t I : T T r e n d s a n d R e a s o n s t o G o G r e e nr e n d s a n d R e a s o n s t o G o G r e e n

Datacenters
Networked computers are the backbone of business, but the growth in servers and network
infrastructure has caused a sharp spike in the electrical usage in the datacenter. Power
consumption per rack has risen from 1 kW in 2000 to 8 kW in 2006 and is expected to top
20 kW in 2010, as shown next.

20
18
16
14
12
10
8
6
4
2
0
2000
2006
2010
kWh Per Rack

This 20-fold demand in energy consumption isn’t just due to more servers. A lot of the
increase comes from the additional network infrastructure needed to support additional
servers. Of the US$29 billion spent each year on server power and cooling, just 30 percent
actually goes to the IT load.
Consider a 24-port Ethernet switch. On the low end, it uses 250 watts of power (most
switches use more) and it is in continuous use. Each 1U rack switch uses 2,190 kW each year.
If the electricity generated to power this switch comes from a coal-fired plant, 1,780 pounds
of coal are needed to produce the 2,190 kW, as illustrated next.

Each rack- ...Which then
Switch mounted switch generates...
uses 250 watts of 1,780 pounds Two tons of carbon
power, which of coal dioxide
uses...

Burning 1,780 pounds of coal releases over two tons of carbon dioxide into the atmosphere,
along with other pollutants, such as sulfur dioxide and nitrogen oxide.