I want to know if this is true on the reducer side. Output of all mappers will merge at reducer side. In which location this merge happens? If that location does not have enough space does reducer fail? What is the solution for MapReduce jobs if intermediat results for some keys is more than local disk of reducer?Hadoop the definitive guide says:intermediate results on the mapper side is written to local disk at mapred.local.dir location so if this location does not have enough space the map will fail.