The storage device 1 includes a storage controller 10 and a plurality of SSDs 20.

The storage controller 10 is a control unit that controls read and write of data from and into the SSDs 20. Though the storage controller 10 is duplicated, in the example of the drawing, in order that reliability may be improved by preparation of replicas of data to be read and written, the storage controller 10 may not be duplicated or may be triplicated or further multiplexed.

The storage controller 10 includes a host interface (I/F) 11, a management I/F 12, a disk I/F 13, an accelerator 14, an internal switch 15, a memory 16, and a central processing unit (CPU) 17.

The host I/F 11 communicates with the host devices 2. The management I/F 12 communicates with the management host device 3. The disk I/F 13 communicates with the SSDs 20. The accelerator 14 carries out data reduction processing for reduction in data volume of data to be written into the SSDs 20. As the data reduction processing, compression processing for compression of the data, deduplication processing for exclusion of duplicate data, and the like may be enumerated. Though the accelerator 14 is implemented by dedicated hardware in the example of the drawing, the accelerator 14 may be implemented by software. The internal switch 15 switches connections among units of the storage controller 10.