We use both apache-hadoop-3.1.3 and CDH-6.1.1-1.cdh6.1.1.p0.875250 HDFS in production, and both of them have the memory increasing over -Xmx value.
We use EC strategy to to save storage costs.
This's the jvm options:
The max jvm heapsize is 8GB, but we can see the datanode RSS memory is 48g. All the other datanodes in this hdfs cluster has the same issue.
This too much memory used leads to my machine unresponsive(if enable swap), or oom-killer happens.