Abstract: A method of the present invention duplicates data of a source medium to target media. The source medium is stored ground data and effective data, wherein the ground data are repeated to fill up the source medium and the effective data overwrite some of the ground data. Next, reading data of the source medium and comparing the data to the ground data. If the data are not as same as the ground data, then copy the data to the at least one target medium. If the data are as same as the ground data, then read the next t data of the source medium and repeating the comparing step.