title: How the data is split in Hadoop
body: <p>Does the Hadoop split the data based on the number of mappers set in the program? That is, having a data set of size 500MB, if the number of mappers is 200 (assuming that the Hadoop cluster allows 200 mappers simultaneously), is each mapper given 2.5 MB of data? </p>
  
  <p>Besides,do all the mappers run simultaneously or some of them might get run in serial?</p>