AbstractOn-site generation of renewable (“green”) energy can help to significantly reduce grid (“brown”) energy consumption, and correspondingly the carbon footprint, of datacenters. However, it is challenging to use green energy generated from sources such as solar and wind because energy production is variable. In this paper, we investigate how to manage an interactive service, where response time is a critical performance metric, to maximize the benefits of green energy produced from these sources. Specifically, we design, prototype, and evaluate a distributed structured storage system, GreenCassandra, which is representative of a class of important subsystems underlying many interactive cloud services. Our proposed approach predicts the production of solar energy, and then controls the number of active nodes to manage energy consumption while respecting a response time SLA. When green energy is available, GreenCassandra may activate extra servers to build up slack with respect to the SLA. When using brown energy, GreenCassandra deactivates servers to reduce energy consumption, leveraging any built-up performance slack, while observing constraints imposed by the SLA. Evaluations show that GreenCassandra can use a heuristic green-energy-aware policy to decrease brown energy consumption and cost by up to 28% and 29%, respectively. Further, these savings are very close to those achievable by an optimizationbased policy that has perfect knowledge of future workload and green energy production.
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