How to increase the mappers and reducers in hadoop according to number of instances used to increase the performance?

Question

If I increase the number of mappers and decrease the number of reducers, then is there any difference in the performance (increase/decrease) of any job while execution?

Answer 1

You can increase number of mappers based on the block size and split size. One of the easiest way is to decrease the split size as shown below:

Configuration conf= new Cofiguration();
//set the value that increases your number of splits.
conf.set("mapred.max.split.size", "1020");
Job job = new Job(conf, "My job name");