A memory system includes a memory device including memory blocks, and a controller configured to in response to a program request or a read request for a selected memory block among the memory blocks being received from a host, store first data to which a first logical address is allocated in a cache group, generate a first entry for the first data stored in the cache group, and in response to second data to which the first logical address is allocated being stored in the cache group after the first data is stored in the cache group, generate a second entry for the second data.