A data storage device includes a storage including a buffer zone and a data zone and a controller for exchanging data with the storage by allocating at least one zone namespace (ZNS) in the data zone, a ZNS being a data storage region that is physically and logically divided and allocated to each of application programs driven in a host. The controller opens one or more sub buffer zones in the buffer zone, divides write data from the host into one or more segments respectively corresponding to sizes of the one or more sub buffer zones, buffers each of the one or more segments in a corresponding one of the one or more sub buffer zones, opens a ZNS corresponding to a length of the write data in the data zone, and migrates the one or more segments buffered in the sub buffer zones to the opened ZNS.