A method performed by a controller of a solid-state drive (SSD) comprising receiving a command from a host, the command identifying a namespace in a non-volatile semiconductor memory device of the SSD to be formatted, identifying a plurality of regions in the non-volatile semiconductor memory device corresponding to the namespace, unmapping a dummy region in a volatile semiconductor memory device of the SSD using invalid addresses, and copying the invalidated dummy region to each region of the plurality of regions of the namespace.