Utility-Function-Driven Energy-Efficient Cooling in Data Centers

Authors:Rajarshi Das, Jeffrey Kephart, Jonathan Lenchner, Hendrik Hamamn

IBM Thomas J. Watson Research Center

Presented by:Shivashis Saha

University of Nebraska-Lincoln

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Outline

• Introduction• Related Work• Data Center Energy Balance• Utility Functions– Multiplicative utility functions– Additive utility functions

• Experiments• Conclusion

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Introduction• Data center energy management– “50% of existing data centers will have insufficient

power and cooling within two years” – “Power is the second-highest operating cost in

70% of all data centers”– “Data centers are responsible for the tens of

millions of metric tons of carbon dioxide emissions annually --- more than 5% of the total global emissions”

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Introduction• Why use autonomic computing?– Large, difficult to manage, complex– Management problem is both qualitatively similar

to and quantitatively harder than that of managing IT alone.

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Contributions

• Apply utility functions to save energy– Tradeoff between energy and temperature– Control parameters:• Fan speed• On/off states of individual Computer Room Air

Conditioning (CRAC)

• Proposed model show 12% reduction in energy without violating temperature contraints

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Related Work

• Saving more energy is not good if administrator does not want that!– Proposed model is flexible

• Apply computational fluid dynamics modeling to complex data center environments

• Temperature aware workload placement based on inlet temperature or heat recirculation

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Data Center Energy Balance• PDC, power to run data center is split using

switch gear equipment into:– Path to power the IT equipments– Path to power the supporting equipments

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Data Center Energy Balance• The support path may include– Power for pumping coolant to and from CRACs to

the chiller and to and from the chiller to the cooling tower

• Power path for IT equipments include– Conversion loss due to the uninterruptible power

supply (UPS) systems– Losses associated with the power distribution PPDU

– The UPS systems are located outside the raised floor area

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• The total power on the floor:

• PIT is the power consumed by the IT equipments• Total CRAC fan power and CDU pump power:

• The relation between fan power PCRACi and relative fan speed Θi

Data Center Energy Balance

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Data Center Energy Balance

• Under steady state condition, the total raised floor power equal to the total cooling power

– The reduced fan speed reduces the air flow:

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Data Center Energy Balance

• All raised floor power needs to be cooled by the chilling system, which required power for refrigeration

– COP: the coefficient of performance of the chiller system (assume, average COP = 4.5)

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Data Center Energy Balance

• Reducing CRAC fan speeds, the fan power is reduced

• This reduces both the raised floor power and the power needed from chiller system

• However, reducing fan speed also increases the server inlet temperature

A tradeoff between energy consumption and the temperature!!!

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Utility Functions

• Data center operators responsible for the physical environment tend not to be concerned about application level performance, e.g. performance, availability, or security

• They are more concerned about cost, energy, temperature, and hardware lifetimes

• There are two CRAC units, whose fan speeds are Θ1 and Θ2

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Utility Functions• Multiplicative utility functions

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Utility Functions

The previous utility function is very harsh!

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Utility Functions• Additive utility functions

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Experiments

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Experiments

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Experiments

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Experiments

Each CRAC was:1. Turned off2. Turned on at lowest speed (60%)3. Turned on at max speed (100%)

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Experiments

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Experiments• Snorkels were placed

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Experiments

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Conclusion

• Use of utility functions in data centers• Total reduction of energy consumption by 14% • Dynamic aspects of utility functions are not yet

considered• Investigation of techniques combining dynamic

workload scheduling with dynamic workload migration

Thanks!