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HDFS Snapshots are read-only point-in-time copies of the file system. Snapshots can be taken on a subtree of the file system or the entire file system. Some common use cases of snapshots are data backup, protection against user errors and disaster recovery.

Using the HdpNnSnpOpTest test, administrators can track administrator- and userinitiated snapshot operations on the HDFS.

Outputs of the test : One set of the results for the Hadoop cluster being monitored

Measurement	Description	Measurement Unit	Interpretation
Allow_snap_oper	Indicates the rate at which Allow Snapshots operations were performed on the HDFS.	Operations/Sec	The Allow Snapshots operation allows snapshots of a directory to be created. If the operation is successful, the directory becomes snapshottable. Superuser privileges are required for performing this operation.
Disallow_snap_oper	Indicates the rate at which Disallow Snapshots operations were performed on the HDFS.	Operations/Sec	The Disallow Snapshots operations disallows the creation of snapshots for a directory. All snapshots of the directory must be deleted before disallowing snapshots. Superuser privileges are required for performing this operation.
Create_snap_oper	Indicates the rate at which Create Snapshots operations were performed on the HDFS.	Operations/Sec	Use this operation to create a snapshot of a snapshottable directory. Owner privilege of the snapshottable directory are required for performing this operation.
Delete_snap_oper	Indicates the rate at which Delete Snapshots operations were performed on the HDFS.	Operations/Sec	This operation deletes a snapshot of a om a snapshottable directory. Owner privilege of the snapshottable directory are required for performing this operation.
Rename_snap_oper	Indicates the rate at which Rename Snapshots operations were performed on the HDFS.	Operations/Sec	This operation renames a snapshot. Owner privilege of the snapshottable directory are required for performing this operation.