US Patent 10191814 Restoring data in a hierarchical storage management system

The present disclosure provides a hierarchical storage management system for storing data. A first controller receives a request to migrate a data item to a first storage tier. The data item is associated with at least an initial object ID. The first controller, in response to the request, generates a new object ID and identifies a first record in a data structure, wherein the initial object ID is identical to an object ID of the first record and to a parent object ID of the first record. The first controller replaces the object ID of the first record with the new object ID, creates in the data structure a new record that is associated with the data item, sets an object ID of the new record and a parent object ID of the new record to the initial object ID, and stores the data item to the first storage tier.