question Re: When Reducer Operation actually starts..I mean with respect to Copy Phase ?After completion of copy phase or while copy phase is going on??? in Archives of Support Questions (Read Only) https://community.cloudera.com/t5/Archives-of-Support-Questions/When-Reducer-Operation-actually-starts-I-mean-with-respect/m-p/98885#M12209 <P><A rel="user" href="https://community.cloudera.com/users/1146/bsuresh.html" nodeid="1146">@suresh bonam</A> One of the best answers <A href="http://stackoverflow.com/questions/11672676/when-do-reduce-tasks-start-in-hadoop">http://stackoverflow.com/questions/11672676/when-d...</A></P><P>Reducers start shuffling based on a threshold of percentage of mappers that have finished. You can change the parameter to get reducers to start sooner or later.</P><P>Why is starting the reducers early a good thing? Because it spreads out the data transfer from the mappers to the reducers over time, which is a good thing if your network is the bottleneck</P> Sun, 13 Dec 2015 05:16:40 GMT nsabharwal 2015-12-13T05:16:40Z When Reducer Operation actually starts..I mean with respect to Copy Phase ?After completion of copy phase or while copy phase is going on??? https://community.cloudera.com/t5/Archives-of-Support-Questions/When-Reducer-Operation-actually-starts-I-mean-with-respect/m-p/98884#M12208 <A rel="user" href="https://community.cloudera.com/users/140/nsabharwal.html" nodeid="140">@Neeraj Sabharwal</A> Sat, 12 Dec 2015 22:33:59 GMT https://community.cloudera.com/t5/Archives-of-Support-Questions/When-Reducer-Operation-actually-starts-I-mean-with-respect/m-p/98884#M12208 bsuresh 2015-12-12T22:33:59Z Re: When Reducer Operation actually starts..I mean with respect to Copy Phase ?After completion of copy phase or while copy phase is going on??? https://community.cloudera.com/t5/Archives-of-Support-Questions/When-Reducer-Operation-actually-starts-I-mean-with-respect/m-p/98885#M12209 <P><A rel="user" href="https://community.cloudera.com/users/1146/bsuresh.html" nodeid="1146">@suresh bonam</A> One of the best answers <A href="http://stackoverflow.com/questions/11672676/when-do-reduce-tasks-start-in-hadoop">http://stackoverflow.com/questions/11672676/when-d...</A></P><P>Reducers start shuffling based on a threshold of percentage of mappers that have finished. You can change the parameter to get reducers to start sooner or later.</P><P>Why is starting the reducers early a good thing? Because it spreads out the data transfer from the mappers to the reducers over time, which is a good thing if your network is the bottleneck</P> Sun, 13 Dec 2015 05:16:40 GMT https://community.cloudera.com/t5/Archives-of-Support-Questions/When-Reducer-Operation-actually-starts-I-mean-with-respect/m-p/98885#M12209 nsabharwal 2015-12-13T05:16:40Z Re: When Reducer Operation actually starts..I mean with respect to Copy Phase ?After completion of copy phase or while copy phase is going on??? https://community.cloudera.com/t5/Archives-of-Support-Questions/When-Reducer-Operation-actually-starts-I-mean-with-respect/m-p/98886#M12210 <P><A rel="user" href="https://community.cloudera.com/users/1146/bsuresh.html" nodeid="1146">@Suresh Bonam</A> are you still having issues with this? Can you accept best answer or provide your own solution?</P> Wed, 03 Feb 2016 23:36:51 GMT https://community.cloudera.com/t5/Archives-of-Support-Questions/When-Reducer-Operation-actually-starts-I-mean-with-respect/m-p/98886#M12210 aervits 2016-02-03T23:36:51Z