Home > Storage > PowerScale (Isilon) > Product Documentation > Data Efficiency > Next-Generation Storage Efficiency with Dell PowerScale SmartDedupe > SmartPools and SmartDedupe
SmartDedupe does not deduplicate files that span SmartPools node pools or tiers, or that have different protection levels, access patterns, or caching configurations set. This is to avoid potential performance or protection asymmetry, which could occur if portions of a file live on different classes of storage.
However, a deduplicated file that is moved by SmartPools to a different pool or tier retains the shadow references to the shadow store on the original pool. Retaining the shadow references breaks the rule for deduplicating across different disk pool policies but is less impactful than rehydrating files that are moved. Further deduplication activity on that file no longer references any blocks in the original shadow store. The file must be deduplicated against other files in the same disk pool policy. If the file had not yet been deduplicated, the deduplication index might have knowledge about the file and assess that it is on the original pool. This will be discovered and corrected when a match is made against blocks in the file.
Because the moved file has already been deduplicated, the deduplication index has knowledge of the shadow store only. Because the shadow store has not moved, it will not cause problems for further matching. However, if the shadow store is moved as well (but not both files), a similar situation occurs and the SmartDedupe job will discover this and purge knowledge of the shadow store from the deduplication index.