1) Identifying directories usage in HDFS
Try to run below for each directory to know the usage
[root@abc01 ~]# hadoop fs -du -s -h <hdfs location>
50.9 M /abc
2) namenode heap size is increasing and is around 80 - 90%.
NN heap size increasing because of your cluster is occupying maximum space in HDFS for files & directories.
Here is the link for increaseing values based on file size
I hope this will help you.