If the Hadoop services are running slow in a Hadoop cluster, what would be the root cause for it and how will i identify it?

[#1]

@pavan p

1. First we need to check which component is responding slow (DataNode, NameNode ....etc).

2. We will need to get the PID of that process and collect 5-6 thread dumps during slowness. Please refer to the following article to know how to collect Thread dump along with the CPU data for the slowness analysis.

https://community.hortonworks.com/articles/72319/how-to-collect-threaddump-using-jcmd-and-analyse-i....

3. We will also need to see the Memory utilization/GC pause of those HDFS components. For that we should take a look at the GC log of those components. Also in the logs of NameNode/DataNode we will find th JVMUtil logging if Garbage Collection Pause is too high.

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