Hi all,
Is it true that Hadoop 'always' starts same map tasks multiple times in
order to be fault tolerant. i.e. same task is launched on several
machines so that even if a node fails then same task would be available
on other node. And in case no node fails redundant task that finishes
late is killed. If it is true how can I change that configuration for
Hadoop to do it or not do it.
Speculative execution on the other hand does what I explained above
(redundant map tasks) but only after all the map tasks are scheduled and
if some nodes are free it starts redundant map tasks for those which are
running slow. Is it always true? How do change this configuration
enable/disable.
I am using Hadoop-1.1.2 incase version matters.
I really appreciate if someone could help me with this. Thank you.
Regards
Sundeep
