Radim, In this case, it doesn't matter how many mappers you provide in your job configuration. Hadoop will only give 1 mapper per split. Since your files are less than 64MB (assuming you're using the default block size of HDFS), you only have 2 splits. If you really need more mappers, you need to create smaller input files.
Paragraph 1 under the Map heading on this page explains it as well: http://wiki.apache.org/hadoop/HadoopMapReduce Justin 2011/11/9 Radim Kolar <h...@sendmail.cz>: > I have 2 input seq files 32MB each. I want to run them on as many mappers as > possible. > > i appended -D mapred.max.split.size=1000000 as command line argument to > job, but there is no difference. Job still runs on 2 mappers. > > How split size works? Is max split size used for reading or writing files? > > it works like this?: set maxsplitsize, write files and you will get bunch > of seq files as output. then you will get same number of mappers as input > files. >
