I have 2 DataNodes and both are live. However, the dashboard shows that the HDFS Disk Usage is n/a, and capacity is zero (see the screenshot). I tried to put some files to hdfs through "hadoop fs -put hello.txt /", and got the error File /hello.txt._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1). There are 2 datanode(s) running and no node(s) are excluded in this operation. I guess this means the NameNode knows the existence of 2 DataNodes, and none is excluded from the "-put" operation? I have checked the "dfs.datanode.data.dir", and it is pointing to the correct directory with 500G available space. How can I resolve this issue? ... View more