Embodiments of the invention relate to writing servo patterns having aligned phases onto a recording disk in a process to write the servo patterns onto the disk. In one embodiment, time aligned patterns are written onto a magnetic disk on the basis of time intervals between base patterns with timings aligned to each other throughout tracks on the disk. The time aligned patterns are written onto typically servo tracks at time intervals Ts with aligned timings. Then, on the basis of these time aligned patterns, product servo patterns are written onto the disk. A time aligned pattern is written onto the disk after the lapse of a predetermined write time period since detection of a base pattern corresponding to the time aligned pattern. The write time period is determined on the basis of time intervals between base patterns on adjacent tracks.