Patent ID: 7359927

Claim:
A method for transferring a copy of data stored at a source to a remote location, comprising: (a) storing at the source a first one of a sequence of sets of changes in the data stored at the source; (b) designating in the source a first one of a pair of storage volumes at the remote location as a target for storage therein of the first one of the stored sets of data changes; (c) transferring to the targeted first one of a pair of storage volumes the first one of the stored sets of data changes while leaving in storage at the source the first one of the sets of data changes; (d) designating in the source a second one of a pair of storage volumes at the remote location as a target for storage therein of the first one and a second subsequent one of the sets of changes in data in the sequence thereof, (e) transferring to the targeted second one of a pair of storage volumes the first one of the stored sets of data changes and the second subsequent one of the sets of changes in data in the sequence thereof while leaving in storage at the source said the first one of the sets of data changes and the second subsequent one of the sets of changes in data in the sequence thereof; (f) determining from the remote location whether there has been an error in the transferring to the targeted second one of a pair of storage volumes the first one of the stored sets of data changes and the second subsequent one of the sets of changes in data in the sequence thereof while leaving in storage at the source said the first one of the sets of data changes and a second subsequent one of the sets of changes in data in the sequence thereof; (g) in the absence of an error being determined, removing the first one of the stored sets of data changes and designating in the source the first one of a pair of storage volumes at the remote location as a target for storage therein of the second one and a third subsequent one of the sets of changes in data in the sequence thereof; (h) transferring to the targeted first one of a pair of storage volumes the second subsequent one of the stored sets of data changes and the third subsequent one of the sets of changes in data in the sequence thereof while leaving in storage at the source said the second and third subsequent one of the sets of changes in data in the sequence thereof; and (i) in the absence of an error being determined, removing the second one of the stored sets of data changes and designating in the source the second one of a pair of storage volumes at the remote location as a target for storage therein of the third one and a fourth subsequent one of the sets of changes in data in the sequence thereof.