Home > Storage > PowerScale (Isilon) > Product Documentation > Data Efficiency > Next-Generation Storage Efficiency with Dell PowerScale SmartDedupe > Snapshots and SmartDedupe
SmartDedupe does not deduplicate the data stored in a snapshot. However, you can create snapshots of deduplicated data. If a snapshot is taken of a deduplicated directory, and then the contents of that directory are modified, the shadow stores are transferred to the snapshot over time. Thus, running deduplication before enabling snapshots saves more space on a cluster.
If deduplication is enabled on a cluster that already has a significant amount of data stored in snapshots, deduplication will take time to affect the snapshot data. Newly created snapshots will contain deduplicated data, but older snapshots will not.
It is also good practice to revert a snapshot before running a deduplication job. Restoring a snapshot will cause many of the files on the cluster to be overwritten. Any deduplicated files are reverted to normal files if they are overwritten by a snapshot revert. However, once the snapshot revert is completed, deduplication can be run on the directory again and the resulting space savings will persist on the cluster.
Deduplication of writable snapshot data is not supported. SmartDedupe ignores the files under writable snapshots.