A memory system may include a storage device and a controller. The storage device may include a non-volatile memory device. The controller may include a device memory. The controller may control operations of the non-volatile memory device in accordance with a request of a host device. wherein the controller includes a map data management circuit configured to cache one or more segments from a plurality of map segment groups stored in the storage device, each segment having information including a reference count and mapping relationships between logical addresses and physical addresses, detect, among the one or more cached segments, an upload target segment in which the reference count is greater than a predetermined count and transmit, when a predetermined number or greater of upload target segments are detected within a first map segment group, the predetermined number or greater of upload target segments to the host device.