Patent ID: 7921179

Claim:
A system for changing storage of a shared data set from a current owner storage system to a new owner storage system, each storage system accessing the shared data set, the system comprising: at least one computer processor; a memory device: the current owner storage system configured for storing the shared data set and receiving and performing write requests on the shared data set, the current owner storage system comprising: a current owner migration module stored in the memory and configured for: at time t 0 , beginning transmitting an image of the shared data set to the new owner storage system over a network; after beginning transmitting the image at time t 0 , between time t 0 and time t 1 , receiving and performing write requests on the shared data set and producing a change log for each write request that describes a change to the shared data set caused by performance of the write request, time t 1 being after time t 0 ; at time t 1 , receiving a first message from the new owner storage system, time t 1 comprising an approximate point in time that transmission of the image to the new owner storage system is completed; in response to receiving the first message at time t 1 , beginning transmitting the change logs, produced between time t 0 and time t 1 , to the new owner storage system over the network; after beginning transmitting the change logs, between time t 1 and time t 2 , receiving write requests to the shared data set, not performing the received write requests on the shared data set, and producing a record of each received write request, time t 2 being after time t 1 ; at time t 2 , receiving a second message from the new owner storage system, time t 2 comprising an approximate point in time that transmission of the change logs to the new owner storage system is completed; and in response to receiving the second message at time t 2 , transmitting the records of write requests, produced between time t 1 and time t 2 , to the new owner storage system over the network.