Go to name node UI and you can check if the newly added data nodes has any blocks or not. By default HDFS will not write or copy data to the newly added nodes. you need to run HDFS balancer to distribute the data among all datanodes
2. Go to HDFS > INSTANCES and then click on HOSTS column or service column to sort out datanodes and the nodes that run DN.
3. GO to IMPALA > INSTANCES and sort it as per above point