Density; Cooling; Power - Compaq BL10e - HP ProLiant - 512 MB RAM Introduction Manual

Density

Density, the amount of throughput that can be provisioned into a given rack footprint, was one of the
earliest problems to be recognized. A focus on density in the late 1990's led to the emergence of 1U
rack-mount servers such as the HP ProLiant DL360 and DL160 servers. With the recent explosion of
Web 2.0, cloud computing, and the general scaling of enterprise requirements, density will remain
important. HP continues to improve overall density with BladeSystem servers and specialized scale-out
servers. As densities have increased, the focus has shifted to cost efficiency and power and cooling
limitations.

Cooling

With increases in server density come cooling problems. As CPU power rose to over 120 watts per
socket in the early 2000s, the problem of simply moving the heat out of the chassis and subsequently
out of the data center became a serious problem. To understand the magnitude of the problem,
consider that by itself, an x86 processor may operate at 120 Watts/square inch; while an electric
cooktop element may operate at only 40 Watts/square inch. Designers now face the challenging task
of removing this immense heat load from a server which has limited cooling tolerance. At the data
center level, administrators need to view the data center holistically: that is, evaluating the energy
flow from the computer chip inside a server to the cooling tower of the data center.

Power

While closely linked to density and cooling, the challenges surrounding power also include facility
limitations, electricity costs, and overall infrastructure costs. Historically, once a data center reached
its available power limit, administrators had to use more efficient equipment, build a new facility, or
reclaim resources to optimize the existing facility.
Electricity costs have become a significant portion – as much as 40 percent – of the total data center
operating costs. Worldwide, electricity used by servers doubled between 2000 and 2005.
Higher rack densities have caused power and cooling costs to surpass the costs of the IT equipment
and the facility space. Overall infrastructure costs are increasing as data centers become more
mission-critical, requiring additional monitoring and maintenance of redundant power and cooling
equipment.
2 By combining estimates of the annual cost of power with the infrastructure costs, it can be
shown that the result leads to a cost more than the server itself (Figure 1).
1 Koomey, J. "Estimating Total Power Consumption by Servers in the U.S and the World," Stanford University,
February 2007.
2 The Uptime Institute has introduced a simplified data center Infrastructure Cost equation that sums the costs of
raw space with the cost of power and cooling resources. See the technology brief "Data center cooling
strategies", http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01153741/c01153741.pdf
for more details.
3 Belady, C., "In the data center, power and cooling costs more than the IT equipment it supports," Electronics
Cooling, volume 13, No. 1, February 2007.
While energy cost models will fluctuate with the market, the long-term trend for electricity costs is almost
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certainly up, and prudence dictates that both vendors and users consider this as a permanent state of affairs.
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