High reliability and high performance of a storage device formed of a Dual port NVMe SSD are achieved while preventing the risk of destruction of data. The storage device includes a main memory that belongs to each of two or more clusters and that stores data related to an IO request; and a processor belonging to each of the clusters controlling accesses to the main memory. The main memory includes a first region where writing from the memory drive is permitted and a second region where the writing is prohibited. The processor selects the first region as a transfer destination related to the IO request from the memory drive when the IO request is a first request, and selects the second region as the transfer destination related to the IO request from the memory drive while permitting writing to the second region when the IO request is a second request.