Chen, Files are stored based on the reducer partitions, not exactly per-key. The result is that there are far lesser files than you imagine there ought to be. The keys are kept sorted inside the partitioned files and thus you do not lose out on your key groups either.
See Partitioner, which is responsible for doing the partitioning of your map outputs: (http://hadoop.apache.org/common/docs/r0.20.2/mapred_tutorial.html#Partitioner) On Sun, Sep 25, 2011 at 10:30 PM, He Chen <airb...@gmail.com> wrote: > Hi everyone > > According to my understanding of Hadoop, it save MapReduce job's > intermediate results into files in the mapper's hard drive. Each key will > occupy a file. I am curious what will happen if mapper's hard drive does not > have enough inodes to save the generated keys. Because every file needs a > inode. > > Best wishes! > > Chen > -- Harsh J
