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

i am using hadoop 2.2, and don't know how to set max input split size I would like to decrease this value, in order to create more mappers I tried updating yarn-site.xml, and but it does not work

indeed, hadoop 2.2 /yarn does not take of none the following settings

mapreduce.input.fileinputformat.split.minsize
1


mapreduce.input.fileinputformat.split.maxsiz e
16777216



mapred.min.split.size
1


mapred.max.split.size
16777216

best