| 摘要 |
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. |
