Methods and structures for appending metadata with recorded data in a dynamic mapped storage device. In a dynamically mapped storage device in which all user supplied logical blocks are dynamically mapped by the storage device controller to physical disk blocks, features and aspects hereof allow presently unused physical space to be used for storing additional metadata associated with recorded data. As the current capacity ratio of the storage device increases, appending of metadata may cease and previously recorded data including metadata may be re-recorded (migrated) to eliminate the appended metadata. The appended metadata may be used for enhanced diagnosis and analysis of characteristics of the operating storage device and may be used to restore the content of the storage device to an earlier state. The metadata may include, for example, track following position of the read/write head, temperature, head flying height, and time of day.