A disk resident system for managing split data sector information in a headerless format magnetic disk device. The split data sector information is stored in a split data sector information field that is recorded in available areas within a headerless disk format such as the gaps within the headerless disk format or in available space within disk administration fields. Preferred areas within a headerless disk format include the gap immediate preceding a servo burst, the gap immediately following a servo burst, or within the servo burst itself, so that the split data sector information is readily available at the time the servo burst is read and interpreted. Information in a split data sector information field can include various combinations of the number of bytes in a split data sector segment that follows a first servo burst, the number of fixed length full data sectors between the first servo burst and an adjacent second servo burst, and the number of bytes in a split data sector segment that follows the second servo burst. Any split data sector information not expressly represented in a split data sector information field can be calculated because the number of bytes between a pair of adjacent servo bursts is known. Overlapping split data sector information in successive split data sector information fields can be used for look-ahead purposes or data integrity purposes. A split data sector information field can also be accompanied by an ECC type field for data integrity check purposes.