Provided is a storage device of a serial attached small computer system interface/serial advanced technology attachment (SAS/SATA) type, which provides data storage/reading services through an SAS/SATA interface. The SAS/SATA type storage device includes: a memory disk unit which includes a plurality of memory disks provided with a plurality of volatile semiconductor memories; an SAS/SATA host interface unit which interfaces between the memory disk unit and a host; and a controller unit which adjusts synchronization of a data signal transmitted/received between the SAS/SATA host interface unit and the memory disk unit to control a data transmission/reception speed between the SAS/SATA host interface unit and the memory disk unit. The storage device can support a low-speed data processing speed for the host and simultaneously support a high-speed data processing speed for the memory disk unit, so that there are advantages in that the performance of the memory disk can be fully utilized to enable high-speed data processing in an existing interface environment.