Abstract—HFSP: Bringing Size-Based Scheduling To Hadoop. Size-based scheduling with aging has been recog-nized as an effective approach to guarantee fairness and near-optimal system response times. We present HFSP, a scheduler introducing this technique to a real,multi-server,complex and widely used system such as Hadoop. Size-based scheduling requires a < Final Year Projects 2016 > priori job size information, which is not available in Hadoop: HFSP builds such knowledge by estimating it on-line during job execution. Our experiments, which are based on realistic workloads generated via a standard benchmarking suite, pinpoint at a signiﬁcant decrease in system response times with respect to the widely used Hadoop Fair scheduler without impacting the fairness of the scheduler, and show that HFSP is largely tolerant to job size estimation errors.