You can also try decreasing the replication factor for the
intermediate files between jobs. This will make writing those files
faster.
On Apr 8, 2009, at 3:14 PM, Lukáš Vlček wrote:
Hi,
by far I am not an Hadoop expert but I think you can not start Map
task
until the previous Reduce is finished. Saying this it means that you
probably have to store the Map output to the disk first (because a]
it may
not fit into memory and b] you would risk data loss if the system
crashes).
As for the job chaining you can check JobControl class (
http://hadoop.apache.org/core/docs/current/api/org/apache/hadoop/mapred/jobcontrol/JobControl.html)
<http://hadoop.apache.org/core/docs/current/api/org/apache/hadoop/mapred/jobcontrol/JobControl.html
>
Also you can look at https://issues.apache.org/jira/browse/HADOOP-3702
Regards,
Lukas
On Wed, Apr 8, 2009 at 11:30 PM, asif md <[email protected]> wrote:
hi everyone,
i have to chain multiple map reduce jobs < actually 2 to 4 jobs >,
each of
the jobs depends on the o/p of preceding job. In the reducer of
each job
I'm
doing very little < just grouping by key from the maps>. I want to
give the
output of one MapReduce job to the next job without having to go to
the
disk. Does anyone have any ideas on how to do this?
Thanx.
--
http://blog.lukas-vlcek.com/
