1. A method for initializing and operating a file system in a flash memory device comprising; a plurality of physical blocks divided respectively into a meta block storing file information and a data block storing data and having a physical address defined within a physical address range, wherein each meta block comprises a plurality of first regions; wherein the flash memory file system is adapted to map logical blocks to the physical blocks, each logical block having a logical address defined within a logical address range separate from the physical address range; the method comprising: programming the flash memory file system to divide the logical blocks into logical groups, wherein the number of logical groups is equal to a common difference value greater than 1; storing erasure data for one of the logical groups in one of the first regions of the meta block; upon receiving a task request for a data file corresponding to at least one of the logical groups, and for each of the at least one of the logical groups: loading erasure data for only a current logical group into an external memory device; and, mapping the logical blocks of the current logical group to the physical blocks in accordance with the erasure data loaded into the external memory device; and, storing data of the data file in the data block of the flash memory device in accordance with the mapping of the logical blocks to the physical blocks.