In federation cases, if we have a config like below:
When the folder hdfs://nn2-clusterx.example.com:8020/projects/footarget is not actually exist, the command hdfs dfs ls / can still see the folder, but the folder is not actually exist. then we try to use mkdir command to create the viewfs folder hdfs dfs mkdir /foo, the return code is true, but the folder is not created. However, when we use hdfs dfs mkdir -p /foo/xxx which have a deeper location to create folder, the folder is successfully created. The results in these two cases may be ambigiuous.