Patent ID: 7478211

Claim:
A method for copying storage, comprising: receiving, at a first unit, data updates from a second unit; storing the data updates in a plurality of physical storage locations associated with the first unit, wherein the received data updates are stored only once in the plurality of physical storage locations associated with the first unit; and generating links to at least one of the plurality of physical storage locations to achieve consistent data between the first unit and the second unit, wherein the method further comprises: (i) determining if the stored data updates form a consistency group, prior to generating the links, wherein the consistency group is a set of data updates in which the set of data updates corresponds to a plurality of storage volumes, wherein the set of data updates must be written together in order to maintain mutual data consistency among data included in each storage volume of the plurality of storage volumes; (ii) determining the at least one physical storage location that commits the consistency group, wherein virtual storage associated with the first unit links to the determined at least one physical storage location, wherein a consistency group pointer table includes entries for a virtual block and a physical block; and (iii) releasing unlinked physical storage locations to be used for storing subsequent data updates, wherein the first unit is a secondary storage control, wherein the second unit is a primary storage control, wherein the secondary storage control and the primary storage control comprise a plurality of storage controls, and wherein in response to receiving an error while waiting for all links to be updated, performing for each storage control of the plurality of storage controls being processed: (a) determining, by a replication management application, if selected links correspond to a current consistency group for the storage control being processed; and (b) reverting the selected links to correspond to a previous consistency group, in response to determining by the replication management application that the selected links correspond to the current consistency group for the storage control being processed.