1. A second storage system that is connected to a computer and a first storage system including a first storage device, the second storage system comprising: a first control section that is connected to the computer; a second control section that includes a second storage device that stores data to be used by the computer and a cache memory, and controls an input/output of data to the second storage device and the cache memory; a third control section that is connected to the first storage system; and an internal network that mutually connects the first control section, the second control section and the third control section, wherein the first control section receives from the computer a first input/output request having first identification information indicative of a storage device to be accessed, and selects one of the second control section and the third control section to which a second input/output request based on the first identification information is sent.