Hi Loakim: Sorry, your hypothesis doesn't make sense. I would suggest you to read the "Learning HBase Internals" by Lars Hofhansl at http://www.slideshare.net/cloudera/3-learning-h-base-internals-lars-hofhansl-salesforce-final to understand how HBase locking works.
Regarding to the issue you are facing, are you sure you configure the job properly (i.e. requesting the jobtracker to have more than 1 mapper to execute)? If you are testing on a single machine, you properly need to configure the number of tasktracker per node as well to see more than 1 mapper to execute on a single machine. my $0.02 Jerry On Tue, Sep 4, 2012 at 11:17 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. > > Does this "lock" hypothesis make sense? Is there any way I could avoid > this useless delay? > > Thanks in advance and regards, > Ioakim >
