A data storage device may include: a controller, including a host memory and a device memory, configured to communicate with a host, wherein one or more host unit regions, having a first size, are allocated to the host memory; and a storage including a nonvolatile memory device. The controller may include a map data manager configured to store map data in the storage, the map data including a mapping relationship between logical addresses of the host and physical addresses of the data storage device, configured to group the logical addresses into logical address groups so that the total size of map data for each of the logical address groups corresponds to the first size, and manage a reference count for each of the logical address groups.