1. A method for mapping between physical element addresses of a media library and a set of contiguous logical element addresses comprising: establishing a base logical element address for an element type; associating each physical element address from a set of physical element addresses for elements of the element type with an index value from an index of sequential index values, wherein at least one physical element address in the set of physical element addresses is not contiguous with the next physical element address in the set of physical element addresses; and for each physical element address from the set of physical element addresses, determining a corresponding logical element address based on an associated index value for that physical element address and the base logical element address.