title: Does hadoop mapreduce open temporary files in hdfs
body: <p>When a map-reduce job runs, it must be creating a lot of temporary files for storing results of various mappers and reducers. Are those temporary files written to hdfs. </p>
  
  <p>If yes, the namenode's editlog could become huge in a short time given that it records each and every transaction like file open, close etc. Can that be avoided by directly writing to the native filesystem instead of hdfs or is that a bad idea?</p>