When Reducer Operation actually starts..I mean with respect to Copy Phase ?After completion of copy phase or while copy phase is going on???

[#1]

@Neeraj Sabharwal

[#2 · Accepted solution]

@suresh bonam One of the best answers http://stackoverflow.com/questions/11672676/when-d...

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.

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

[#3]

@Suresh Bonam are you still having issues with this? Can you accept best answer or provide your own solution?