Patent ID: 7237079

Claim:
A data migration method which carries out data migration from a first storage device to a second storage device in a computer system, comprising a host computer, said first storage device and said second storage device which provide volumes to said host computer, a switch which establishes connection among said host computer, said first storage device and said second storage device, and a data migration apparatus, wherein, said data method comprising the steps of: (a) providing to said second storage device, a request for creating a destination volume having a size identical to the size of a source volume that is provided by said first storage device; (b) carrying out a data copy processing which copies the data stored in said source volume, which data is comprised of a plurality of data blocks each having a predetermined data length, to said destination volume, by repeating a processing with respect to data in said source volume from top to bottom so that all of the data in the source volume is copied to the destination volume one data block at a time until all of the plurality of data blocks comprising said data stored in said source volume are copied to said destination volume, under a condition that a write complete notification as to data immediately before said data is received from said second storage device, said processing including, to read out data of a predetermined length from said source volume, calculate a write address in said destination volume on the basis of a total data length of the data read out so far from said source volume, and to provide to said second storage device a request for writing the data together with a designation of the write address thus calculated; and (c) providing a connection switching request to said switch and carrying out switching of a target of said host computer, from said first storage device to said second storage device, and wherein said second storage device performs the steps of: (d) creating said destination volume in accordance with the request for creating said destination volume received from said data migration apparatus, (e) comparing the write address designated by the request for writing the data to said destination volume, which is received from said data migration apparatus, with a reserved write address of a new data in said destination volume determined by the total data length of data already-written in said destination volume, and (f) executing the write request and issuing a write complete notification to said data migration apparatus if the two addresses equal to each other, and (g) repeating steps (e) and (f) until all of the data blocks comprising the data of the source volume have been copied to the destination volume.