Abstract: Methods and architecture for monitoring hard disk drive operation is provided. The hard disk drive system provided includes a spindle, a head and a disk with a disk medium including a buried servo layer having a first frequency of data on a first track and a second frequency of data on a second track, the second track adjacent to the first track. The method includes the steps of writing a wide track pattern having a predetermined frequency on a track of a hard disk drive medium, generating a readback signal by reading the pattern from the track, processing the readback signal by mixing the readback signal with a reference signal to obtain a mixed signal having a summed signal and a difference signal, and filtering the mixed signal by a filter centered around the difference signal to generate a measurement signal corresponding to a relative speed change of the spindle and a head-to-disk motion.