A method is disclosed for reducing disk expansion effects while writing spiral
reference patterns on a disk. The disk drive comprises control circuitry and a
head disk assembly (HDA). In the method, an external spiral servo writer is used
to control a radial location of the head for writing a plurality of the spiral
reference patterns in an order such that at least two of the spiral reference patterns
are not written temporally sequential to an adjacent spiral reference pattern.
The head internal to the disk drive is used to read the spiral reference patterns
in order to write product servo bursts to the disk, thereby defining a plurality
of radially spaced, concentric data tracks.