If a split is bigger than a specified size, it will be splitted again. If a split is smaller than a specified size, it will be combined with others, we can name the combining procedure regroup. The combining is logic, it's not necessay to combine these smaller splits to a disk file, which will not affect the performance.The target is that every task spent same time running. [image: mbr_detailedx.JPG]
2010/2/6 jian yi <[email protected]> > In MR (Map-Reduce) model, reducings are not balanced, because the scale of > partitiones are unbalanced. How to balance? We can control the size of > partition, rehash the bigger parition and combine to the specified size. If > a key has many values, it's necessary to execute mapreduce twice.The > following is the model digram: > > [image: Map-Balance-Reduce.JPG] > > Scheduler can regard a task as a timeslice similarly OS scheduler. > >
