Patent ID: 7536444
Filing Date: 2009-05-19
Classification: G06F

Abstract:
1. A remote copying method in a remote copying system, the remote copying system comprising: a first site that includes a plurality of first site logical storage areas, the first site sending data for which write requests are issued to the first site logical storage area, and a second site that includes a plurality of second site logical storage areas and that receives the data, the remote copying method including the steps of: for consistency between order of the write requests and reflection order of the data in the second site on the second site logical storage area, providing a plurality of consistency groups, each comprised of a group of the first site logical storage areas in the first site, that send and receive the data using respective independent sequence numbers regarding an order of the write requests of pairs of the first site logical storage area and the second site logical storage area, and the second site reflects the data that is received regarding the group of first site logical storage areas in each of the consistency groups of which the sequence numbers are uniform, on the second site logical storage area, and performing a composition change of the group of the first site logical storage areas comprising a selected at least one of the consistency groups, wherein the second site starts a reflection operation of the data belonging to the at least one selected consistency group on the second site logical storage area, which data is sent in response to one of the write requests by the first site after the composition change, after reflection of specific data sent in response to one of the write requests by the first site on the second site logical storage area before the composition change, wherein the composition change is migration from a first consistency group to a second consistency group of a specific pair among the pairs, the selected consistency group is the second consistency group, and the specific data is the final data sent in response to the write request by the first site immediately before the composition change in the first consistency group, wherein the first site turns on a migration source flag for the final data in the first consistency group sent in response to the write reguest by the first site immediately before the migration of the specific pair from the first consistency group to the second consistency group, wherein the first site turns on a migration target flag for the first data for the second consistency group sent in response to one of the write requests immediately after the migration of the specific pair from the first consistency group to the second consistency group, wherein, after turning on the migration source flag and the migration target flag, the first site assigns a sequence number of data for the specific pair for the second consistency group to be the same sequence number or a higher sequence number than the sequence number of the first data for the second consistency group immediately after the migration of the specific pair, wherein the second site checks to see if formalization of all data in the second consistency group, prior to the data for which the migration target flag has been turned on, is complete, and when it is determined that formalization is complete for all data prior to the data for which the migration target flag has been turned on, the second site starts formalization of the first data for which the migration target flag has been turned ON.