Disclosed is a method and apparatus embodying a flash translation layer (FTL) in a storage device including a flash memory. The FTL may classify a block into a sequential group and a fusion group based on a locality of a write request. The FTL may store data in blocks of the fusion group by using a page mapping scheme, and sequentially store data by using a block mapping scheme. The FTL may improve efficiency of garbage collection operation that is performed by using limited redundant blocks and also may increase efficiency of a non-sequential reference operation.