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

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 2

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 Variable 3 Solar power Workload Source? Storage?

Outline Motivation Parasol – Solar-powered micro-datacenter GreenSwitch – Manage workload and energy sources GreenSwitch results Conclusion 4

Parasol 16 solar panels: 3.2kW 2 inverters: DCAC Installed on the roof Steel structure Small container IT equipment 2 racks 64 Atom servers 2 switches 3 PDUs 16 lead-acid batteries: 32kWh 2 charge controllers: Off-grid, DCAC 5

Electrical infrastructure Charge Controller Inverter Electrical Panel DC AC DC AC Power grid AC 6 IT Equipment

Example energy source management Charge Controller Inverter Electrical Panel DC AC DC AC Power grid AC Time Power 7 IT Equipment

Example energy source management Charge Controller Inverter Electrical Panel DC AC DC AC Power grid AC Time Power 8 IT Equipment

Example energy source management Charge Controller Inverter Electrical Panel DC AC DC AC Power grid AC Time Power 9 IT Equipment

Possible energy source management Power Time Basic 10

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 ParasolGreenSwitch Perform changes Get status 11

GreenSwitch GreenSwitch architecture Predictor Battery Charge Level Workload Prediction Energy Availability Prediction Solver Energy Source Schedule Workload Schedule Configurer Parasol Time Power Brown Price Solar Time Power Workload Use solar to power all servers Charge battery with surplus solar Workload Model & MILP 12

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) 13

Experimental environment 14 SWIM: Facebook based workload [MASCOTS11] IT load

Parasol without GreenSwitch Green use Green available Net metering Brown use IT load 66% cost savings Solar amortized in 7 years 15

GreenSwitch: non-deferrable workload Battery discharge Battery charge IT load 75% cost savings Batteries cannot be amortized Peak grid power 16 Green useBrown use Green available

GreenSwitch: deferrable workload Battery discharge Battery charge IT load Net metering 96% cost savings Solar + batteries amortized in 7.6 years 17 Green available Green use

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 18

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… 19

Parasol and GreenSwitch: Managing Datacenters Powered by Renewable Energy Íñigo Goiri, William Katsak, Kien Le, Thu D. Nguyen, and Ricardo Bianchini

Fewer conversions – Grid-tie: ACDC Low conversion losses 21 Commodity hardware – Availability – Cheaper Cheaper transmission

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 22

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 23

Other results Energy storage – Batteries – Net metering pricing Peak grid power charges Solar availability – Cloudy, sunny, rainy… Other workloads – Nutch Grid outage 24