hdfs data node disconnected from namenode

Question

I get from time to time the following errors in cloudera manager:

This DataNode is not connected to one or more of its NameNode(s). 

and

Answer 1

I realize you took some steps to test this, but intermittent disconnects still make it sound like a Connectivity issue.

If nodes really don't come back after a disconnect, that may be a configuration issue, which could well be completely independent from the reason why they disconnect in the first place.