We have a 100 node hadoop cluster that is used for multiple purposes. I want to run few mapred jobs and I know 4 to 5 slaves should be enough. Is there anyway to restrict my jobs to use only 4 slaves instead of all 100. I noticed that more the number of slaves more overhead there is.
Also can I pass in hadoop parameters like mapred.child.java.opts so that the actual child processes gets the specified value for max heap size. I want to set the heap size to 2G instead of going with the default..