Information processing device, external storage device, host device, relay device, control program, and control method of information processing device

An storage device connected to a information processing device, the storage device comprising:

• readable and writable nonvolatile memory;
• an interface controller connected to the information processing device, the interface controller enabling a first interface controller for supporting read and write operations of the nonvolatile memory and a second interface controller for supporting only the read operation of the read and write operations of the nonvolatile memory to be alternately selected;
• and
• a control unit for determining whether or not a shift condition for causing the nonvolatile memory to shift to a read only mode in which only the read operation of the read and write operations is carried out is met, and switching the interface controller from the first interface controller to the second interface controller when the shift condition is met, wherein
• when the storage device determined to be recognized as read only memory is connected to information processing device, the storage device selects the second interface controller, whereby
• the information processing device recognizes the storage device as a read only memory without issuing a write request to the storage device.