Parasol and GreenSwitch:Managing Datacenters Powered by Renewable

Energy

Íñigo Goiri, William Katsak, Kien Le,Thu D. Nguyen, and Ricardo Bianchini

Department of Computer Science

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Motivation• Datacenters consume large amounts of energy• High energy cost and carbon footprint– Brown electricity: coal and natural gas

• Connect datacenters to green sources: solar, wind

Apple DC in Maiden, NC 40MW solar farm

Green datacenter

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Challenges and opportunities

• Scheduling workload/energy sources– Lower costs: brown energy, peak brown power, capital

• Study opportunities in green datacenters– Build hardware/software

Power

Time

Load

VariableSolar power

Workload

Source?

Storage?

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Outline

• Motivation• Parasol– Solar-powered micro-datacenter

• GreenSwitch– Manage workload and energy sources

• GreenSwitch results• Conclusion

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Parasol16 solar panels: 3.2kW2 inverters: DC→AC

Installed on the roof• Steel structure• Small container

IT equipment• 2 racks• 64 Atom servers• 2 switches• 3 PDUs

16 lead-acid batteries: 32kWh2 charge controllers: Off-grid, DC↔AC

http://parasol.cs.rutgers.edu

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Electrical infrastructure

Charge Controller

Inverter

Electrical Panel

DC

AC

AC

DC

AC

Power grid

AC

IT Equipment

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Example energy source management

Charge Controller

Inverter

Electrical Panel

DC

AC

AC

DC

AC

Power grid

AC

Time

Pow

erIT Equipment

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Example energy source management

Charge Controller

Inverter

Electrical Panel

DC

AC

AC

DC

AC

Power grid

AC

Time

Pow

erIT Equipment

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Example energy source management

Charge Controller

Inverter

Electrical Panel

DC

AC

AC

DC

AC

Power grid

AC

Time

Pow

erIT Equipment

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Possible energy source managementPo

wer

Time

Basic

Maximizing benefits is complex

Each time slot:• Weather conditions• Brown energy price• Peak brown power price• Battery charge level• Active servers• Workload slack

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GreenSwitch• Minimize brown electricity cost

– Brown energy– Peak brown power– Battery lifetime constraint

• Manage energy sources– Use solar/net metering– Charge/discharge battery– Limit brown peak power

• Manage workload– Turn servers on/off– Delay deferrable jobs

Parasol

GreenSwitch

Perform changesGet status

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GreenSwitch

GreenSwitch architecture

Predictor

Battery Charge Level

Workload Prediction

Energy Availability Prediction

Solver

Energy Source Schedule

Workload Schedule

Configurer

Parasol

TimePo

werBrownPrice

Solar

Time

Pow

er

Workload

Use solar to power all serversCharge battery with surplus solar

Workload

Model & MILP

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Experimental environment

• Evaluation on 64 Parasol nodes– 12 one-day experiments– Deferrable vs. non-deferrable workloads– Baseline datacenter (no solar, no batteries, no delays)

• New Jersey brown electricity pricing– On/off-peak energy, peak power, net metering

• GreenSwitch for Hadoop (configurer)

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Experimental environment

SWIM: Facebook based workload [MASCOTS’11]

IT load

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Parasol without GreenSwitch

Green use

Green available

Net metering

Brown use

IT load

66% cost savings → Solar amortized in 7 years

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GreenSwitch: non-deferrable workload

Battery dischargeBattery chargeIT load

75% cost savings → Batteries cannot be amortized

Peak grid power

Green use Brown use

Green available

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GreenSwitch: deferrable workload

Battery discharge

Battery charge

IT load

Net metering

96% cost savings → Solar + batteries amortized in 7.6 years

Green available

Green use

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Parasol: a real system

• Real software running on real hardware• Power losses• Overhead of energy source switching• System limitations– Net metering vs. Battery charging– Use brown vs. Net metering– Green battery charging vs. Use brown

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Conclusions

• Green datacenters– Challenges & opportunities– Hardware/software solution

• GreenSwitch benefits– Delaying load and solar gives the best results– Reduces amortization time by 1.8-2x– Flexibility: no batteries, workloads, wind…

http://parasol.cs.rutgers.edu

Parasol and GreenSwitch:Managing Datacenters Powered by Renewable

Energy

Íñigo Goiri, William Katsak, Kien Le,Thu D. Nguyen, and Ricardo Bianchini

http://parasol.cs.rutgers.edu

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• Fewer conversions– Grid-tie: AC→DC

• Low conversion losses

• Commodity hardware– Availability– Cheaper

• Cheaper transmission

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Parasol: lessons learned

• Not cheap– Flexibility adds complexity and cost– Placement on the roof– Full monitoring

• Not easy– Complete design– Dealing with facilities, companies, and vendors– Mistakes are easy– Delays, delays, and more delays

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Viability of green datacenters

• Example companies investing in self-generation– Apple, Microsoft, McGraw-Hill

• Research shows cost savings• Getting more attractive– Space: Solar panels are getting more efficient– Cost: 7x cheaper than 30 years ago– Governmental Incentives

• Grid-centric: power purchase agreement– Losses, dependence, long term scalability

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Other results

• Energy storage– Batteries– Net metering pricing

• Peak grid power charges• Solar availability– Cloudy, sunny, rainy…

• Other workloads– Nutch

• Grid outage