Importance

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Abstract

The invention relates to snapshots of a data storage system including a host that communicates with a cache memory, source storage, target storage, and metadata, including a source storage for active data, a target storage to store migrated snapshot data, first metadata (e.g., bitmaps and log files with pointers) to indicate when and where the first snapshot data is in target storage, and second metadata (e.g., bitmaps and log files pointers) to indicate when and where the second snapshot data is in target storage where the first and second metadata locate the same snapshot data in the target storage. The invention maintains data consistency when reading metadata for snapshots into host memory, searching the metadata to identify snapshots that require original data to be destaged, destaging the original data to target storage, and updating the metadata to locate the original data and indicate completion of the target destage operation.

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First Claim