Patent ID: 8156279

Claim:
A flash memory controller for use in a flash memory module, wherein the flash memory module includes at least one flash memory chip for providing a storage area, wherein the storage area includes a physical unit memory area, and wherein the physical unit memory area includes a prescribed management information storage area, wherein the flash memory controller controls reading and writing of data from and into the at least one flash memory chip, wherein the flash memory controller performs deduplication processing by storing logical addresses of one or more corresponding logical unit memory areas in the prescribed management information storage area, wherein the one or more logical unit memory areas are associated with the physical unit memory area, and wherein the number of said physical unit memory areas storing identical data is defined as X, the total number of valid logical addresses stored in the management information storage areas of the physical unit memory areas storing the identical data is defined as Y, the maximum number of said logical addresses that can be stored in the management information storage area is defined as n, and the smallest integer not less than (Y/n) is defined as Z, wherein if a difference of X and Z is equal or greater than a prescribed value, the flash memory controller eliminates duplicated data by storing the identical data to unused physical unit memory areas, in which a number of the unused physical unit memory areas is equal to Z.