1. A flash file system, comprising: a flash memory; and a subsystem interfacing between the flash memory and a host system, the subsystem including, a host system interface interfacing with the host system; a cache memory system, the cache memory system having a storage capacity of a number of data units, and storing data for transfer to and from the host system via the host system interface based on logical addresses received from the host system via the host system interface, the data being stored in association with the logical addresses; a flash translation layer unit mapping a logical address received from the cache memory into a physical address of the flash memory; and a flash memory interface interfacing with the flash memory to transfer data to the flash memory from the cache memory system based on the physical address received from the flash translation layer unit and to transfer data from the flash memory to the cache memory system based on the physical address received from the flash translation layer unit.