Patent ID: 7725668

Claim:
A computer system comprising: a first storage system having a first volume for storing data sent from a host system; and a second storage system having a second volume for storing said data sent from said first storage system; wherein said first storage system comprises a data transfer unit for transferring said data stored in said first volume to said second volume of said second storage system; wherein said second storage system comprises a snapshot creation unit for creating a snapshot of said second volume in a third volume based on a snapshot creation command and a memory storing copy control information including information which indicates whether said transfer of the data from said first volume to said second volume is being performed; and wherein when said snapshot creation unit receives said snapshot creation command, said snapshot creation unit checks whether said transfer of the data from said first volume to said second volume is being performed by referring to the copy control information; wherein when said transfer of the data from said first volume to said second volume is being performed, said snapshot creation unit suspends performing said snapshot creation, and wherein when said transfer of the data from said first volume to said second volume is finished, said snapshot creation unit starts to perform said snapshot creation.