Patent ID: 8738963

Claim:
A system comprising: a first storage system including: a first port to receive I/O operations from a host computer; a first storage controller including a first processor and a first memory; and a plurality of first storage devices, which stores data received from the host computer, and a second storage system including: a second port to receive I/O operations from the host computer via the first storage controller; a second storage controller including a second processor and a second memory; and a plurality of second storage devices, which stores data received from the host computer, wherein a plurality of error check codes corresponding to data stored in the plurality of second storage devices are stored in the first storage system, and wherein, when the first storage system receives an I/O operation from the host computer to read first data of a virtual volume, where the first data is stored in the second storage system, the first storage system decides whether to check for an error of the first data stored in the second storage system by using the first error check codes of the plurality of error check codes stored in the first storage system depending on whether or not the first data is already stored in the first storage system as a replica copy.