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MapReduce workloads have evolved to include increasing amounts of time-sensitive, interactive data analysis; we refer to such workloads as MapReduce with Interactive Analysis (MIA). Such workloads run on large clusters, whose size and cost make energy efficiency a critical concern. Prior works on MapReduce energy efficiency have not yet considered this workload class. Increasing hardware utilization helps improve efficiency, but is challenging to achieve for MIA workloads. These concerns lead us to develop BEEMR (Berkeley Energy Efficient MapReduce), an energy efficient MapReduce workload manager motivated by empirical analysis of real-life MIA traces at Facebook. The key insight is that although MIA clusters host huge data volumes, the interactive jobs operate on a small fraction of the data, and thus can be served by a small pool of dedicated machines; the less time-sensitive jobs can run on the rest of the cluster in a batch fashion. BEEMR achieves 40-50% energy savings under tight design constraints, and represents a first step towards improving energy efficiency for an increasingly important class of datacenter workloads.

Erasure codes such as Reed-Solomon (RS) codes are being extensively deployed in data centers since they offer significantly higher reliability than data replication methods at much lower storage overheads. These codes however mandate much higher resources with respect to network bandwidth and disk IO during reconstruction of data that is missing or otherwise unavailable. Existing solutions to this problem either demand additional storage space or severely limit the choice of the system parameters.In this paper, we present Hitchhiker, a new erasure-coded storage system that reduces both network traffic and disk IO by around 25% to 45% during reconstruction of missing or otherwise unavailable data, with no additional storage, the same fault tolerance, and arbitrary flexibility in the choice of parameters, as compared to RS-based systems. Hitchhiker "rides" on top of RS codes, and is based on novel encoding and decoding techniques that will be presented in this paper. We have implemented Hitchhiker in the Hadoop Distributed File System (HDFS). When evaluating various metrics on the data-warehouse cluster in production at Facebook with real-time traffic and workloads, during reconstruction, we observe a 36% reduction in the computation time and a 32% reduction in the data read time, in addition to the 35% reduction in network traffic and disk IO. Hitchhiker can thus reduce the latency of degraded reads and perform faster recovery from failed or decommissioned machines.