As mentioned previously, should a map fail to copy one of its inputs, there will be several side-effects.
Unless -overwrite is specified, files successfully copied by a previous map will be marked as “skipped” on a re-execution.
If a map fails mapreduce.map.maxattempts times, the remaining map tasks will be killed (unless -i is set).
If mapreduce.map.speculative is set final and true, the result of the copy is undefined.
