Victim segments to be returned to a free area in a segment cleaning process from a plurality of segments included in each segment group are selected by using a method corresponding to the segment group. A host comprises an interface relaying data exchange with a storage device; and a file system module performing a segment cleaning process by selecting victim segment from a plurality of segments stored in the storage device, discovering live blocks in each of the victim segments, writing back the discovered live blocks to the storage device through the interface, and returning the victim segments to a free area. The file system module calculates victim points for all segments included in a first segment group using a first victim point calculation formula, calculates victim points for all segments included in a second segment group using a second victim point calculation formula, and selects the victim segments based on the victim points.