Disclosed is a method of writing data in a storage device including a nonvolatile memory device. The method includes receiving write data with a write request, detecting a number of free blocks, if the detected number of free blocks is less than a threshold value, allocating a log block only in accordance with a sub-block unit, but if the detected number of free blocks is not less than the threshold value, allocating the log block in accordance with one of the sub-block unit and a physical block unit, wherein the sub-block unit is smaller than the physical block unit.