Hello guys, we are running CDH 4.7.1 with CM 4.8.5 and we have pools set in fair schedular using CM's mapreduce configurations.
One of the pools is set with following thresholds
Can you compare that information to the JT web UI and check the cluster summary and the number of occupied slots etc.
There is also a FS eventlog which can show you what the scheduler is doing. See the really old hadoop fair scheduler information.
You do know that CDH 4 is almost EOL and that you should move to CDH 5 and YARN and are planning for that (I hope).