21.6. Creating a Snapshot of Hadoop enabled Red Hat Storage Volumes

The Red Hat Storage Snapshot feature enables you to create point-in-time copies of Red Hat Storage volumes, which you can use to protect data and helps in disaster recovery solution. You can directly access Snapshot copies which are read-only to recover from accidental deletion, corruption, or modification of their data.
For information on prerequisites, creating, and restoring snapshots, see Chapter 12, Managing Snapshots. However, you must ensure to stop all the Hadoop Services in Ambari before creating snapshot and before restoring a snapshot. You must also start the Hadoop services again after restoring the snapshot.
You can create snapshots of Hadoop enabled Red Hat Storage volumes and the following scenarios are supported:
Scenario 1: Existing Red Hat Storage trusted storage pool

You have an existing Red Hat Storage volume and you created a snapshot of that volume but you are not yet using the volume with Hadoop. You then add more data to the volume and decide later that you want to rollback the volume's contents. You rollback the contents by restoring the snapshot. The volume can then be enabled later to support Hadoop workloads the same way that a newly created volume does.

Scenario 2: Hadoop enabled Red Hat Storage volume

You are running Hadoop workloads on the volume prior to the snapshot being created. You then create a snapshot of the volume and later restore from the snapshot. Hadoop continues to work on the volume once it is restored.

Scenario 3: Restoring Subset of Files

In this scenario, instead of restoring the full volume, only a subset of the files are restored that may have been lost or corrupted. This means that certain files that existed when the volume was originally snapped have subsequently been deleted. You want to restore just those files back from the Snapshot and add them to the current volume state. This means that the files will be copied from the snapshot into the volume. Once the copy has occurred, Hadoop workloads will run on the volume as normal.