A data storage system for storing data includes a data storage medium and a data interface that communicates with the data storage medium. The data interface is configured to place data into a logical data capsule having a defined size, where the data placed into the logical data capsule can occupy less than the defined size of the logical data capsule. In the data storage system, the logical data capsule is moved as a whole between the data storage medium and the data interface. Additionally, when any data in the logical data capsule is read or modified, all of the data in the logical data capsule is read or modified as a whole. The data interface is configured to assign a capsule number to a logical data capsule within a first range of capsule numbers or a second range of capsule numbers. The first range of capsule numbers corresponds to a first data access time of the first data storage medium. The second range of capsule numbers corresponds to a second data access time of the second data storage medium. The first and second data access times are different