Data storage method

A data storage method is disclosed for storing user data and segmentation information (47) received from a host onto tape. In addition to writing data words and segmentation data relating to record marks (REC) and file marks (FM), the method provides for the writing of further segmentation information concerning 'save set' marks (SSM) that serve to group the data records into sets that are distinct from the collections of records delimited by file marks. In one embodiment, the data words are stored in fixed-size blocks (39) with segmentation data being recorded in an index (40) that terminates each block. Preferably, file marks (FM) and save set marks (SSM) can be independently written to indicate segmentation after the same record. Furthermore a count of save set marks can advantageously be used to facilitate searching of the tape.