1. Cost and Energy Reduction Evaluation
for ARM Based Web Servers
Olle Svanfeldt-Winter, Sébastien Lafond, Johan Lilius
Sébastien Lafond
sebastien.lafond@abo.fi
13.12.2011 Åbo Akademi University - Department of Information Technologies 1

2. Outlines
Motivations
Energy consumption
Total energy consumption
Energy propositional computing
Data Centers Costs
Evaluated HW
Benchmarks
Results
Conclusion
13.12.2011 Åbo Akademi University - Department of Information Technologies 2

3. Motivations
Energy consumption of data centers is both an
economical and environmental issue
– important impact on the possibility to construct or
expend data centres
– cooling infrastructures are expensive
Models for data centre costs exists
– It is possible to determine the relationship between the
total cost of a data center and the energy consumption of
its server
13.12.2011 Åbo Akademi University - Department of Information Technologies 3

4. Energy consumption
The two main metrics are:
TotalFacilityPower
– PUE = ITequipmentPower
1
– DCiE = ×100
PUE
Both express the energy efficient of the data center
But at the end the total energy consumption matters
– this is what you will pay for every month
– infrastructure design based on the maximum power
dissipation of the data center
13.12.2011 Åbo Akademi University - Department of Information Technologies 4

5. Total energy consumption
According to [1] the processors in a typical server
contributed to:
– 45% of the total power dissipation at peak
performance
– 27% when idle
Power dissipation is application specific, but on
average the dissipation is 72% of the peak power
Google server containers are reported to house
1160 servers and dissipate 250KW each.
[1] L. Barroso and U. Holzle, “The case for energy-proportional computing,” Computer,
vol. 40, no. 12, pp. 33–37, December 2007.
13.12.2011 Åbo Akademi University - Department of Information Technologies 5

6. Energy propositional computing
Ideally the energy consumption of data centers
should be proportional to the required performance
– this is unfortunately far from being true
– energy efficiency is best at peak performance
– however typical servers operate most of
the time at 10 to 50% of their capacity
Using low-end and cheaper processors might be an
answer for better energy proportionality
– increase the granularity of power management steps
13.12.2011 Åbo Akademi University - Department of Information Technologies 6

7. Data Centers Costs
Based on Hamilton analysis [1,2]
• $0,07 per KWh
• 80% average load usage
• 50k servers
• 165 W per server
• 5% cost of money
• 10 year amortization time
• 4 year amortization time for the network
• 3 year amortization time for the server
[1] J. Hamilton, “Cooperative expendable micro-slice servers (cems): Low cost, low power servers for internet-scale
services,” in Proceedings of CIDR 09, January 2009.
[2] “Overall data center costs. http://perspectives.mvdirona.com/2010/09/18/overalldatacentercosts.aspx,” James
Hamilton, September 2010
13.12.2011 Åbo Akademi University - Department of Information Technologies 7

8. Evaluated HW
Versatile Express
– Quad-core Cortex A9
– 1GB DDR2
– 400Mhz
Tegra 250
– Dual-core Cortex-A9
– 1GB DDR2
– 1Ghz
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9. Benchmarks
Autobench and Apache 2 HTTP server
– static web pages
SPECweb2005
– more demanding web services
Erlang
– micro benchmarks
– real world SIP proxy
13.12.2011 Åbo Akademi University - Department of Information Technologies 9

10. Results
Apache
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11. Results
SPECweb2005
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12. Results
Erlang
Calls per dissipated Watt
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13. Conclusion
The performance of 2 ARMv7 based ARM cortex-A9
was measured and evaluated and compared to Xeon
processors
Measurements show that the Cortex A9 can be up
to
– 11 times more efficient with the Apache server
• Enabling a 12,7% total cost saving
– 3.6 times more efficient with Erlang base SIP proxy
• Enabling a 10% total cost saving
– 2.9 times mote efficient with the SPECweb2005
• Enabling a 9% total cost saving
13.12.2011 Åbo Akademi University - Department of Information Technologies 13

14. Questions ?
13.12.2011 Åbo Akademi University - Department of Information Technologies 14