Comment by colinwilson

Systems like Hadoop and Spark will run multiple versions of the same task writing out to a FS at once but to a temporary directory and when the first finishes the output data is just moved to the final place. It's not uncommon for a job to "complete" writing data to S3 and just sit there and hang as the FS move commands run copying the data and deleting the old version. It is just assumed a rename/move is a no-op in some systems.