Patent ID: 7472241

Claim:
A storage system comprising: a first storage apparatus located at a first site; a second storage apparatus located at a second site; a third storage apparatus located at a third site; and a network connecting the first, second, and third storage apparatuses to one another in a communication-enabling manner, wherein, the first storage apparatus stores data transmitted from a host system and transmits the data to the second and the third storage apparatuses, and the first storage apparatus transmits a verification request command upon the first storage apparatus' determination that a predetermined number of storage system access requests has occurred or a predetermined time has been exceeded, the first storage apparatus transmitting the verification request command to at least one of the second and the third storage apparatuses to instruct that a data consistency verification be conducted between the second and the third storage apparatuses; and wherein the second and the third storage apparatuses individually store the data transmitted from the first storage apparatus, and wherein at least one of the second and the third storage apparatuses are adapted to perform consistency verification operations responsive to the verification request command issued from the first storage apparatus, to verify the consistency in the data between the second and third storage apparatuses, wherein the first storage apparatus does not perform any of the consistency verification operations to verify the consistency in the data between the second and third storage apparatuses.