Method, memory controller and storage device to perform garbage collection based on fragmentation ratio of blocks

An operating method of a storage device including a memory device including memory blocks each for storing a plurality of pages, and a memory controller configured to control the memory device, the operating method comprises:

• executing, by the memory controller, operations comprising:
• receiving data and a write request from a host;
• transferring a program command to the memory device;
• writing, through use of the memory device, the data in a memory space and generating valid page information representing whether a page corresponding to the memory space with the data written therein is valid;
• further executing, by the memory controller, operations comprising:
• updating a valid page bitmap representing validity of the plurality of pages based on valid page information received from the memory device;
• calculating, based on the valid page bitmap, a fragmentation ratio representing a segmentation degree between at least one valid page and at least one invalid page of a memory block among the memory blocks;
• and
• performing garbage collection based on the fragmentation ratio.