Provided herein may be a storage device and a method of operating the storage device. A memory controller may include a storage area manager and a write operation controller. The storage area manager may allocate a plurality of memory devices to a first group and a second group in response to a storage area setting command. The write operation controller may control a group selected from the first group and the second group according to a type of a write request to store write data. At least one memory devices in the first group includes memory blocks storing n data bits. At least one memory devices in the second group includes memory blocks storing m data bits.