Where HDFS stores data
The data for hdfs files will be stored in the directory specified in dfs.datanode.data.dir, and the /dfs/data suffix that you see in the default value will not be appended.
If you edit hdfs-site.xml, you'll have to restart the DataNode service for the change to take effect. Also remember that changing the value will eliminate the ability of the DataNode service to supply blocks that were stored in the previous location.
Lastly, above you have your values specified with file:/... instead of file://.... File URI's do need that extra slash, so that might be causing these values to revert to the defaults.