Hi,
Yes this is default behavior (if you're placing the file from within a data node). You can have them distributed by issuing hadoop fs -put command from a client that isn't running DataNode.
According to docs:
* The replica placement strategy is that if the writer is on a datanode,
* the 1st replica is placed on the local machine,
* otherwise a random datanode. The 2nd replica is placed on a datanode
* that is on a different rack. The 3rd replica is placed on a datanode
* which is on the same rack as the first replica.