In HDFS, DataNode supports hot swappable drives. With a swappable drive we can add or replace HDFS data volumes while the DataNode is still running.
The procedure for replacing a hot swappable drive is as follows:
First we format and mount the new drive.
We update the DataNode configuration dfs.datanode.data.dir to reflect the data volume directories.
Run the "dfsadmin -reconfig datanode HOST:PORT start" command to start the reconfiguration process Once the reconfiguration is
complete, we just unmount the old data volume
After unmount we can physically remove the old disks.