Patent ID: 8495014

Claim:
A computer system comprising: a first storage system having a plurality of first drives and a first controller which configures a first volume and a first journal volume on the plurality of first drives, wherein the first controller stores data sent from a host computer to the first volume, and creates journal data including an update number and the data, and stores the created journal data to the first journal volume; a second storage system having a plurality of second drives and a second controller which configures a second volume and a second journal volume on the plurality of second drives, wherein the second controller stores the journal data sent from the first storage system to the second journal volume, and reflects the data in the journal data to the second volume in order of the update number in the journal data stored in the second journal volume; and a third storage system having a plurality of third drives and a third controller which configures a third volume and a third journal volume on the plurality of third drives, wherein the third controller stores the journal data sent from the second storage system to the third journal volume, and reflects the data in the journal data to the third volume in order of the update number in the journal data stored in the third journal volume; wherein when the second controller in second storage system receives a read request of journal data from the third controller in the third storage system, the second controller in second storage system rejects the read request if the second controller has not reflected data included in the requested journal data to the second volume.