International Business Machines Corporation

Donald Lee Miller

Mark Anthony Sovik

Data is rapidly restored from a backup copy, and user access of the restored data further expedited by providing on-demand output of logged changes to the backup data. Contents of the backup data are the same as contents of corresponding primary data at a designated time when the backup data was created. If any changes to the primary data are received by the system after creating the backup copy, the changes are stored by the system in a change log. In one embodiment, where the system stores changes in multiple logs, the logs may be consolidated and sorted according to an appropriate schedule. Whenever primary data becomes unavailable, the system starts to apply logged changes to the backup copy right away, using the consolidated and sorted change log. When the system receives user requests to access the primary data, the system determines whether the log contains any changes that have not been applied to the backup data. If the log contains un-applied changes, the storage system provides the requesting user with an output of the most recent logged change from the log. On the other hand, if the log does not contain any un-applied changes, the storage system provides the requesting user with an output of the requested data from the backup data.

Method and apparatus for rapid data restoration including on-demand output of sorted logged changes

An expedited data backup is performed by creating a duplicate set of pointers to a current dataset already identified by an original pointer set, then designating the dataset as a backup dataset, and thereafter preventing changes to the pointed-to-data and the duplicate pointers, where changes to the current dataset are nonetheless effected by storing new data and modifying the original pointer set alone. More specifically, the backup involves an original dataset having multiple subparts residing at various original storage locations, which are pointed-to by a primary set of pointers. A virtual backup copy is created by duplicating the primary set of pointers to create a backup set of pointers. The backup set of pointers are entered in a backup list, in association with the virtual backup copy and the original dataset. To preserve the backup copy, the system prevents changes to the original dataset and the backup set of pointers. When any changes are directed to subparts of the original dataset, the system creates a changed dataset by storing the changes at one or more change storage locations and updating the primary set of pointers to identify the change storage locations along with any original storage locations still containing unchanged subparts of the original dataset. In addition to expediting data backups, fast data recovery is possible by updating the primary set of pointers to duplicate the backup set of pointers.

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Tucson, AZ, United States of America

Donald Lee Miller