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The "PerformanceTuning" page has been changed by LarsGeorge: http://wiki.apache.org/hadoop/PerformanceTuning?action=diff&rev1=5&rev2=6 You can save a lot of time by enabling JVM re-use on MR jobs. In the JobTracker, or the Job itself, set {{{mapred.job.reuse.jvm.num.tasks}}} to the number of times to reuse a JVM ''for the same map or reduce transform'' -or to -1 to reuse without limits. This reduces JVM startup/teardown times. - The more copies of a block there is, the more places there are to schedule work on the same host as the block, so eliminating the need to copy the block over the network. Set the {{block.replication.factor}} on files to be more than the default (usually 3) if you want to make it accessible in more spaces. + The more copies of a block there is, the more places there are to schedule work on the same host as the block, so eliminating the need to copy the block over the network. Set the {{{block.replication.factor}}} on files to be more than the default (usually 3) if you want to make it accessible in more spaces. == HBase Performance tips ==
