Abstract: Redirecting a data object such as a file block extent. The data object can be redirected from a first memory block to a second memory block, wherein the second memory block includes a copy of modified data of the first memory block. The redirection may occur in response to a request to modify data of the data object. Redirection preserves the prior version of the data object stored in the first memory block to enable restoration of the data object if needed. In one embodiment, a first data object is mapped to a first memory block. A copy of data contents of the first memory block is created. Thereafter, data contained within the copy is modified in accordance, for example, with a request to write data to the first data object. The modified copy is stored in a second memory block, and the first data object is mapped to the second memory block.

Abstract: A system or method for reestablishing data consistency between data volume P and its real time or near real time copy volume S. When volumes P and S enter a state of data inconsistency, data consistency can be restored through use of roll-back and/or roll-forward logs. The roll-forward log stores new data to be written to volume P. The roll-back log stores existing data of volume S before the existing data of volume S is overwritten with new data. As will be more fully described below, the roll-back log can be used to incrementally restore volume S to a prior data state in reverse chronological order, while a roll-forward log can be used to incrementally restore volume S in forward chronological to equal the data state of volume P.

Abstract: A system or method for creating a point-in-time (PIT) or backup copy of one or more data volumes using a roll-back log. The backup copy can be created without employing hot backup mode. In one embodiment, the method includes copying data blocks of a volume to a backup memory configured to store a backup copy of the volume, wherein the data blocks are sequentially copied until all of the data blocks of the volume are copied to the backup memory. A first request is generated to overwrite existing data of a first data block of the volume with new data before all of the data blocks of the volume are copied to the backup memory. Before overwriting the existing data and before all of the data blocks of the volume are copied to the backup memory, the existing data is copied to a first memory (e.g., the roll-back log). Before all of the data blocks of the volume are copied to the backup memory, the existing data is overwritten with the new data.

Abstract: A roll-back memory can be used to incrementally restore one or more data volumes in reverse chronological order to the data state they occupied at some prior point in time without using a backup copy. After the one or more data volumes have been restored in reverse chronological order, a roll-forward memory can be used to incrementally restore the one or more data volumes in forward chronological order to the data state they occupied at some other point in time without using a backup copy. Incrementally restoring the one or more data volumes in reverse chronological order may follow an incremental restoration of the one or more data volumes in forward chronological order and vice versa until the one or more data volumes are in the data state they occupied just prior to, for example, a data corruption event.

Abstract: A method and system of replicating data using a recovery data change log. According to one embodiment a method is provided in which a copy of a data change log at a primary node is maintained at a data recovery node, the data change log being associated with a primary data volume of the primary node, a failure of the primary data volume is detected, and a secondary data volume of a secondary node is updated using the copy of the data change log in response to the detection.