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MapReduce has emerged as a prevailing distributed computation paradigm for enterprise and large-scale data-intensive computing. The model is also increasingly used in the massively-parallel cloud environment, where MapReduce jobs are run on a set of virtual machines (VMs) on pay-as-needed basis. However, MapReduce jobs suffer from performance degradation when running in the cloud due to inefficient resource allocation. In particular, the MapReduce model is designed for and leverages information from the native clusters to operate efficiently, whereas the cloud presents a virtual cluster topology overlying or hiding actual network information. This results in two placement anomalies: loss of data locality and loss of job locality, where jobs are placed physically away from their data or other associated jobs, adversely affecting their performance.In this paper we propose, CAM, a cloud platform that provides an innovative resource scheduler particularly designed for hosting MapReduce applications in the cloud. CAM reconciles both data and VM resource allocation with a variety of competing constraints, such as storage utilization, changing CPU load and network link capacities. CAM uses a flow-network-based algorithm that is able to optimize MapReduce performance under the specified constraints -- not only by initial placement, but by readjusting through VM and data migration as well. Additionally, our platform exposes, otherwise hidden, lower-level topology information to the MapReduce job scheduler so that it makes optimal task assignments. Evaluation of CAM using both micro-benchmarks and simulations on a 23 VM cluster shows that compared to a state-of-the-art resource allocator, our system reduces network traffic and average MapReduce job execution time by a factor of 3 and 8.6, respectively. |
