What's the purpose of a setup and cleanup task?

[psdc1978 <ps...@gmail.com>]

Hi,

I would like to understand what's the purpose of a setup and cleanup task.

During the start-up of the job tracker, it will be assigned 2 setup tasks
and 2 cleanup tasks for map and for the reduce. My questions are:

- What's the purpose of a setup task?

- The setup class runs on the jobtracker side or on the tasktracker side?

- If I set around 50 map tasks to run in my hadoop example, will only one
setup task initiate all map activities? (The same question for the reduce
side)


The above questions are also for the cleanup task.


Regards,
-- 
Pedro