Abstract: Point-in-time backup copies of a production volume that include volume maps between adjacent source and target volumes can be created in a cascade of data volumes. An empty volume map having the backup copy as the target can be created. The empty volume map can include a first bitmap used to indicate that data is stored in the source or the target, a second bitmap for use in managing and optimizing background copying, and an index for tracking a status of background copying. The volume map can be populated so that the first bitmap indicates data is stored in the source, and the index set to a start value. Production volume data regions can be sequentially background copied to the backup copy, while tracking using the index. Upon backup copy completion, the values of the volume map having the backup copy as the target can be stored.

Abstract: Point-in-time backup copies of a production volume that include volume maps between adjacent source and target volumes can be created in a cascade of data volumes. An empty volume map having the backup copy as the target can be created. The empty volume map can include a first bitmap used to indicate that data is stored in the source or the target, a second bitmap for use in managing and optimizing background copying, and an index for tracking a status of background copying. The volume map can be populated so that they first bitmap indicates data is stored in the source, and the index set to a start value. Production volume data regions can be sequentially background copied to the backup copy, while tracking using the index. Upon backup copy completion, the values of the volume map having the backup copy as the target can be stored.

Abstract: A first data storage device receives a first write request from a host device to update a first subset of the data regions and sends the first write request to a second data storage device. Prior to receiving a notification from the second device that it has been updated in accordance with the first write request, the first device receives a second write request from the second device to update a second subset of the data regions and one of the two devices is selected. If the first device is selected, the first device updates only its data regions that are in the second subset but not in the first subset according to the second write request. In the case that the second device is selected, the first device updates its data regions that are in the second subset according to the second write request.

Abstract: An apparatus, method, and computer program for facilitating disaster recovery of a first computer system, wherein first data residing on a first storage device associated with the first computer system is recoverable from second data residing on a second storage device associated with a second computer system and wherein the second storage device is operable to have an associated state of powered up or powered down. A receiver receives an update operation for updating the second storage device. A processor updates anon-volatile storage means with the update operation, prior to update of the second storage device, wherein the non-volatile storage means is associated with the second computer system.

Abstract: An apparatus, method, and computer program for facilitating disaster recovery of a first computer system, wherein first data residing on a first storage device associated with the first computer system is recoverable from second data residing on a second storage device associated with a second computer system and wherein the second storage device is operable to have an associated state of powered up or powered down. A receiver receives an update operation for updating the second storage device. A processor updates anon-volatile storage means with the update operation, prior to update of the second storage device, wherein the non-volatile storage means is associated with the second computer system.

Abstract: A storage controller includes an interface to host computer apparatus and an interface to a plurality of controlled storage apparatus. The storage controller comprises a host write component operable to send a request to write a data object to a source data image at one of said plurality of controlled storage apparatus; a copy component operable in response to a metadata state to control copying of said data object to a target data image in a delimited sequence of data images in a cascade at said plurality of controlled storage apparatus and a fill-in component operable in response to detection of an offline condition of a disk containing said target data image to control substitution of a fill-in disk in place of said disk containing said target data image.

Abstract: A method and apparatus is disclosed in which a storage controller cooperable with a host and a plurality of controlled storage is provided to localize an impact of a failure to a target disk in an affected segment. The storage controller includes a host write component to write a data object to a source image storage; a first copy component responsive to a first metadata state to control copying of the data object to a first target storage; a second copy component responsive to a second metadata state to perform either: copying the data object to a second target or causing the first copy component to copy the second target to the first target; and a third copy component to control cascaded copying of the data object to a third target storage. Either the second or the third copy component controls cascaded copying of a delimited data image subsequence responsive to a metadata state indicating currency of a data grain in either the second or the third target.

Abstract: An apparatus achieves data communications between a data storage controller and data storage devices within a data storage system via an optical network. The apparatus includes a wavelength division multiplexing logic for simultaneously establishing, on the optical network, a number of arbitrated communications loops between the controller and the data storage system, for communicating data between the controller and the storage devices.