A storage device with multiple storage units, which is applicable to a system end. The storage device is a hard disk drive (HDD) or solid state disk (SSD) with a standard size. The storage device includes a first storage unit and at least one memory storage unit. The memory storage unit and the first storage unit serve to back up and update each other. The storage device further includes a multiplex control unit and a power control unit connected to the multiplex control unit. According to the decision of the multiplex control unit, the power control unit controls turning on/off of the first storage unit and the memory storage unit.