Importance

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Abstract

The present invention is directed to systems and methods for hierarchical storage management. A system manager specifies policies used to migrate and recall data from between the local and a remote storage while the system itself is afforded latitude in complying or violating these policies. As a violation of the migration policy, the system of the present invention pre-migrates data from local storage to remote storage prior to the time that a given file will become eligible for migration thereto. During pre-migration, data resides in both local and remote storage. Once the time for migration has arrived, local storage space may be freed bv simply deleting the data stored locally and retaining the data stored remotely. As part of the recall policy, data is delayed from returning to local storage from the remote storage unless an access request or a write command specifically requires that the data be returned. Mechanisms are disclosed to detect if I/O requests that occur after data has been pre-migrated but before the data has been migrated invalidate the pre-migration.

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First Claim