I was running multi MapReduce jobs at the same time for testing and I noticed that the jobs would map all the maps Tasks on all the jobs before any reduce tasks would start. Then when the reduce task started they all started at the same time. I would thank that on the reduce job would spread out the task to slaves and the next job would start maping with the extra free slaves.
This would not be a good thing if a cluster receives a lot of MapReduce jobs all day long as all the maps would run and the users would have to wait for all the map jobs to be done befor the reduce jobs would start. this could be hours to days depending on the jobs. Please let me know if this is a bug or intended route for some reasion I am not aware of. I am running 0.14.1 version. Billy
