Hadoop 2.0 also added a new capability: taking a snapshot (read-only copy and copy-on-write) of the filesystem (data blocks) stored on the data nodes. Using Snapshots, you can take a copy of directories seamlessly using the NameNode's metadata of the data blocks. Snapshot creation is instantaneous and doesn't require interference with other regular HDFS operations.

The following is an illustration of how snapshot works on specific directories: