International Business Machines Corporation

Storage Technology Corporation

David A Serls

Christopher James West

Patrick James Tomsula

Michael Wayne White

A storage system and method for storing delta difference data indicative of the differences between new data and old data. A data transferring unit has copies of old data and new data. The data transferring unit compares the new data with the old data to determine delta difference data indicative of the differences between the new data and the old data. A target storage device having a copy of the old data receives the delta difference data from the data transferring unit. The target storage device stores the delta difference data and may then determine the new data by merging the old data with the delta difference data. The target storage device transmits the determined new data to a data receiving unit upon request. The method and system may be used with peer-to-peer remote copy (PPRC) storage system and storage area network (SAN) storage system.

Method and system of storing a main data file and deltas in a storage device for determining new data files from the main data file and the deltas

A method and system for transferring difference data (delta) between new and old data from a data transferring unit to a storage device having a copy of the old data for enabling the storage device to determine the new data based on the old data and the transferred difference data and then store the new data in place of the old data. Both of the data transferring unit and the target storage device have a copy of the old data. When new data is written at the data transferring unit to modify the old data the data transferring unit compares the new data with the old data to determine the difference data. The difference data is indicative of the differences between the new data and the old data. The target storage device merges the old data with the difference data to determine the new data. Upon determining the new data the target storage device discards the old data and stores the new data. The method and system may be used with peer-to-peer remote copy (PPRC) storage systems and storage area network (SAN) storage systems.

Method and system for transferring delta difference data to a storage device

A method and system in accordance with the present invention provides additional addressable space on a disk for use by a host processor using a virtual data storage subsystem. The method and system includes defining at least one of a plurality of extended image devices on a disk and requesting an instant image to be addressed to an extended image device utilizing channel command words by a host processor. The method and system also includes reading the instant image utilizing commands, such as channel command words or common descriptor blocks, by the host processor. In a method and system in accordance with the present invention, a plurality of extended image devices are defined as extensions of a primary functional device. Data may be transferred between at least one of the plurality of extended images and the primary functional device, or between at least one of the plurality of extended image devices and another of the plurality of extended image devices. An advantage of a method and system in accordance with the present invention is the availability of additional addressable space which may be used by the host processor for accomplishing the subsystem's functions, such as the copying of track pointers. By extending the amount of addressable space, the host processor is alleviated from having to conduct a search for available space within a primary functional device whenever space on the device becomes scarce.

Method and system for providing additional addressable functional space on a disk for use with a virtual data storage subsystem

The present invention provides a method and apparatus for setting up a Peer-to-Peer Remote Copy (PPRC) session and snapshot copying a remote secondary volume to another volume on the remote subsystem. The apparatus includes a primary storage subsystem having a primary data-storage device with at least a primary volume. A primary processing unit relays a request to perform a snapshot copy of at least a portion of the primary volume to a secondary storage subsystem. The secondary storage subsystem includes a secondary data-storage device having a secondary volume which is maintained in a duplexed state with the primary volume through the use of remote copy sessions. A secondary processing unit, responsive to the relayed request can perform an equivalent of a snapshot copy of at least a portion of the primary volume by making a snapshot copy of a corresponding portion of the secondary volume.

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Littleton, CO, United States of America

David A Serls