Data center operators are touting metrics like PUE to
demonstrate energy efficiency leadership, but there is more to
consider. Data centers exist because they can more efficiently and
economically scale to house servers that host online services used
by enterprises and consumers. However, we need a more holistic
approach to ensure that we are minimizing the energy consumed to
run these services. Performance matters, but so does the energy
consumed to deliver that performance. During my past 40 years as a
computer architect, I have seen processor power grow faster than
processor performance.
During the last decade, processor power had reached extremely
high levels. Previously, when I was a senior server platform
architect at Intel, I led the effort to use low power mobile cores
for server processors. In my role as a cloud server infrastructure
designer at Microsoft for the last five years, I have been focused
on driving our performance per watt higher with each new
generation. Microsoft works closely with our processor suppliers to
specify and test low power processors. We have moved away from
using the highest performance processors because their performance
per watt has been worse than the low power processors. Yes, Every
Watt Matters!
Microsoft remains focused on performance per dollar per watt as
an additional means of achieving higher energy efficiency. The
chart below illustrates how low power processors can indeed provide
a better value proposition.
The performance, price, and power numbers are based upon public
information that was available to us in 2009. In a truly
distributed computing environment, where each server does not need
to deliver the maximum possible performance, the servers with the
best performance per dollar per watt are the best choice. We
continue to favor multi-core processors that are optimized for
performance per watt.
Microsoft maintains some of the most monitored and measured data
centers in the industry. The data provided in the accurate
monitoring of all the aspects of our data centers are combined to
inform a thoughtful and holistic design approach for our
infrastructure and the servers together. This has led to
significant improvements in energy efficiency year-over-year. Our
measurements of server performance under load and workload analysis
at huge scale has also enabled us to right-size our server
platforms. We have eliminated unnecessary components to eliminate
the power they consume, used Gold-rated or better high-efficiency
power supplies and voltage converters, and bounded the
expandability of server platforms to achieve significant power
savings.
More recently, we started using solid state drives in some of
our server platforms where we saw a 30 percent increase in
performance at a five percent increase in power. Additionally, we
have taken advantage of Moore's Law to increase the number of cores
from two per processor in 2007 to eight per processor in 2012,
while maintaining or decreasing platform power. Our holistic
approach, to designing data centers and servers together, has
allowed us to drive additional improvements in energy
efficiency.
Our team of data center designers continue to drive our Power
Usage Effectiveness (PUE) lower and we run our servers at higher
temperatures that allow us to use free air cooling in many of our
locations today. Climate data from The Green Grid shows that free
air cooling can be used exclusively in many places. Because many
systems can run at higher temperatures without problems, using
outside air to cool computing equipment is not only viable, but
also sustainable and cost efficient. The addition of evaporative
cooling also allows operation of our servers when the outside
temperature goes above the 90° to 95° Fahrenheit (F) inlet that the
equipment needs. Evaporative cooling is especially well suited for
climates where the air is hot and humidity is low.
While the standard maximum recommended temperature for data
centers under guidelines from the American Society of Heating,
Refrigeration, and Air-Conditioning Engineers (ASHRAE) is 80.6° F,
there is growing evidence that facilities can operate at
significantly higher temperatures, (ASHRAE now defines an Allowable
A2 range of up to 95° F), without damaging the IT equipment. Most
server manufacturers do warranty their equipment up to 95 °F.
Raising the operating temperature of facilities will result in
significant savings in energy consumption by eliminating the use of
chillers. Since 2007, we have been helping to drive the industry to
open temperature ranges beyond those recommended and shared our
best practices and R&D results from our "data center in a tent project" in 2008.
We have been running our Dublin data center with free air cooling
since 2009 and continue to make improvements with each new phase of
construction.
The free air cooling approach pioneered in our Dublin facility
is also being used at our new sites in Boydton, VA and Des Moines,
IA with an expanded normal operating temperature range up to 85° F
with occasional excursions to 90° F.
Last year, we started deploying
ITPACs in our Quincy, Washington data center. We took 480V
directly from the facility transformers to the server racks,
thereby eliminating losses in another level of voltage conversion.
Furthermore, we also removed the fans from the servers and relied
on the air handlers in the ITPAC to pull the hot air out. Strictly
speaking, this meant that our PUE increased because the fan-less
servers consumed less power! But we were more energy efficient
because it took less total energy to run the same workload!
Our cloud infrastructure server engineering team continues to
work with our technology providers to help them define and design
more energy efficient products with and for us. It is all about
performance per watt. Since 2008, we have been sharing our best practices and ideas for the future with the industry at
large. We also are continuing to participate in industry conferences and share ideas with other
cloud service companies, including Facebook's Open Compute
Project.
We are confident about this direction meeting the needs of our
data center environment and we hope that these best practices helps
to set the stage for continued healthy and dynamic dialog and
sharing in this industry. We are delighted to see eBay's announcement about their plans to use about
six million watts of power generated on-site by fuel cells. We are
looking forward to seeing additional information on the analysis
that led to this bold move. Fuel Cells and other innovative energy
technologies have been on our
research agenda. We will follow the eBay project with great
interest along with other members of the Data Center
Pulse Group and commend eBay for pushing the envelope with this
revolutionary approach and look forward to future progress
reports.
//db
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