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courses:mapreduce-tutorial:step-9 [2012/01/25 16:07]
straka 		courses:mapreduce-tutorial:step-9 [2012/01/25 16:18]
straka
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 Every Hadoop option has a read-only default. These are overridden by cluster specific options. Lastly, all of these are overriden by job specific options given on the command line (or set using the Java API). Every Hadoop option has a read-only default. These are overridden by cluster specific options. Lastly, all of these are overriden by job specific options given on the command line (or set using the Java API).
  
-==== Mapping of Perl options to Hadoop ====+===== A brief list of Hadoop options ===== 
 +^ Hadoop option ^ Default value ^ Description ^ 
 +| ''mapred.job.tracker'' | ? | Cluster master | 
 +| ''mapred.reduce.tasks'' | 1 | Number of reducers | 
 +| ''mapred.min.split.size'' | 1 | Minimum size of file split in bytes | 
 +| ''mapred.max.split.size'' | 2%%^%%63-1 | Minimum size of file split in bytes | 
 +| ''mapred.map.tasks.speculative.execution'' | true | If true, then multiple instances of some map tasks may be executed in parallel | 
 +| ''mapred.reduce.tasks.speculative.execution'' | true | If true, then multiple instances of some reduce tasks may be executed in parallel | 
 +| ''mapred.compress.map.output'' | false | Should the outputs of the maps be compressed before being sent across the network. Uses SequenceFile compression | 
 + 
 +A more complete list (but not exhaustive) can be found [[http://hadoop.apache.org/common/docs/r1.0.0/mapred-default.html|here]]. 
 + 
 +===== Mapping of Perl options to Hadoop =====
 ^ Perl options ^ Hadoop options ^ ^ Perl options ^ Hadoop options ^
 | no options \\ (running locally) | ''-Dmapred.job.tracker=local'' \\ ''-Dmapred.local.dir=hadoop-localrunner-tmp'' \\ ''-Dhadoop.tmp.dir=hadoop-localrunner-tmp'' | | no options \\ (running locally) | ''-Dmapred.job.tracker=local'' \\ ''-Dmapred.local.dir=hadoop-localrunner-tmp'' \\ ''-Dhadoop.tmp.dir=hadoop-localrunner-tmp'' |
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 | ''-c cluster_machines'' | configuration of new cluster contains \\ ''-Dmapred.job.tracker=cluster_master'' | | ''-c cluster_machines'' | configuration of new cluster contains \\ ''-Dmapred.job.tracker=cluster_master'' |
 | ''-r number_of_reducers'' | ''-Dmapred.reduce.tasks=number_of_reducers'' | | ''-r number_of_reducers'' | ''-Dmapred.reduce.tasks=number_of_reducers'' |
 +

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