Patent ID: 7519851

Claim:
A storage system comprising: a first storage system; a second storage system; a plurality of first physical storage devices located in the first storage system; a plurality of second physical storage devices located in the second storage system; and a first controller in the first storage system operative to: store information about first logical devices and second logical devices, the first logical devices being mapped to the first physical storage devices, the second logical devices being mapped to the second physical storage devices; receive a write request containing write data; store the write data in one or more of the first logical devices; generate sequence information indicative of the sequence by which the write data is written to the first logical devices, thereby preserving the write order of data written to the first logical devices; send the write data to the second storage system in accordance with the sequence information such that the write data is stored in one or more of the second logical devices absent write-order determination by the second storage system; receive information from the second storage system about first logical devices and second logical devices following a failure of the first storage system; determine data to be mirrored and one or more second logical devices at which the data to be mirrored is stored based upon the information received from the second storage system; create a virtual volume corresponding to each of the one or more second logical devices at which the data to be mirrored is stored; initiate a copy operation through which the data to be mirrored is copied from each virtual volume to a first logical device at the first storage system; and update the information about first logical devices and second logical devices when the copy operation is successfully completed.