A server including a first storage unit, a control unit, and a host is provided. The first storage unit enters a first sleep mode or a second sleep mode according to a first control signal. When operating in the first sleep mode, the storage unit has a first power consumption value. When operating in the second sleep mode, the storage unit has a second power consumption value that is different from the first power consumption value. The control unit adjusts the first control signal according to a switching signal. The host generates the switching signal according to an access state of the first storage unit.