1. A storage control unit that, upon receipt of a write access request from an external unit, performs control of writing of data that is the subject of the write access request to a storage unit including a plurality of storage devices, the storage control unit comprising: a power supply unit that supplies power from a power source; a battery that stores power so that power can be supplied; a cache memory constituted by a volatile memory capable of storing data when supplied with power; a non-volatile memory capable of continuing to store data even without power supplied thereto, saving dirty data stored in said cache memory when failure of the power supply unit is detected; a request reception unit that receives the write access request when supplied with said power; a first data control unit that controls to store data that is the subject of said write access request in said cache memory as cache data; a determination unit that determines whether or not an amount of dirty data, of said cache data in said cache memory, that has not been reflected to said storage unit, exceeds a prescribed threshold value; a second data control unit that, if the determination is that said prescribed threshold value has been exceeded, controls to store at least a portion of said dirty data of said cache memory in said storage unit; a power source monitoring unit that detects a voltage abnormality of the power that is supplied from said power supply unit; a shared memory that stores configuration information and control information; a save storage unit that saves in said non-volatile memory the dirty data stored in said cache memory on receipt of supply of said power from said battery, if said voltage abnormality is detected by said power source monitoring unit, wherein when the save storage unit saves in said non-volatile memory the dirty data stored in said cache memory, the configuration information and the control information corresponding to the saved dirty data is also saved; and a power source supply control unit that maintains supply of power to said cache memory and said save storage unit using the power from said battery if said voltage abnormality is detected by said power source monitoring unit.