Storage device, controlling method of storage device, and storage device controller having predetermined management information including face attribute information, a controller number, and transition method information

In a storage device according to the present invention, controllers each having a cache memory manage duplication of cache data. A storage device SD includes multiple controllers 1 each including a cache memory, and multiple storing units 21 used by the controllers and configured with logical volume 24 for being provided to a higher-level device 3. Each of the controllers, in a case where a paired destination controller forming a duplication pair is blocked, selects a new paired destination controller for each logical volume, forwards the cache data stored in the cache memory included in the own controller to the new paired destination controller, and stores the cache data in a cache memory included in the new paired destination controller to duplicate the cache data.