On Tue, Sep 4, 2012 at 8:17 AM, Ioakim Perros <[email protected]> wrote: > Hello, > > I would be grateful if someone could shed a light to the following: > > Each M/R map task is reading data from a separate region of a table. > From the jobtracker 's GUI, at the map completion graph, I notice that > although data read from mappers are different, they read data sequentially - > like the table has a lock that permits only one mapper to read data from > every region at a time. >
Your mapreduce job is actually running on the cluster and not in a single thread local (as Jerry hints above). St.Ack
