I know that the result of a Map-phase is an intermediate result which would be the input for a reduce-phase.
Recently, I read in hadoop definitive guide that "results of Map-tasks are stored in disk (i.e. not in HDFS, as they are an intermediate result) and only the results of Reduce-phase are stored in HDFS ".
So, with the above sentence my understanding is that if there is a Map-task then there should be a reduce task also. Because, as the result of a map-task is just an intermediate result and to store these result to HDFS then there should be a reduce-task. Is my understanding correct?
If my understanding is wrong then can anyone give me a scenario where there can be 1 map task and 0 reduce tasks?