1. An apparatus of managing a file system, comprising: a data storage unit that includes a plurality of data blocks each having a predetermined size that store data; a data information storage unit that stores data information on the data stored in the data blocks; and a control unit that writes the data into an empty space of each data block using the stored data information, wherein the data information storage unit comprises: a block map that comprises information on a total used space of each data block; and a sub block map that comprises information on a use space used by the data stored in the data blocks, wherein the control unit updates the block map and the sub block map in order to allow a user to reference the block map and the sub block map when storing data, wherein the sub-block map comprises a next sub-block ID allocated to a next sub-block corresponding to a set of data within a data block storing data.