PURPOSE: To give an access with high efficiency to the desired stripe, by providing the discrimination information and the gap information at the head of a stripe-shaped storage region and selecting the discrimination information with an input/output device and within the reading period of the gap information.

CONSTITUTION: A gasp G is provided at each head part of data segments SG1W including a data region DT and an error correction code ECC in order to secure the discrimination information ID and the time to analyze the information ID. A magnetic tape device SMT is connected to a processor CC via an input/output controller IOC. The processor CC feeds the number of the stripe stroging a desired data to the device IOC. The device IOC analyzes the information ID which is obtained by driving the device SMT to obtain a desired result and then reads out the data DT following the desired one to transfer it to the processor CC. As a result, an access is possible with high efficiency to a desired stripe, and the load of the processor CC is reduced.