A disk drive is disclosed including a disk having a first and second set
of time-based servo patterns. The first set of time-based servo patterns
comprises a first cyclical pattern that repeats radially over the disk,
and the second set of time-based servo patterns comprises a second
cyclical pattern that repeats radially over the disk, wherein each
cyclical pattern comprises a plurality of timing marks. One of the first
cyclical patterns overlaps at least part of a first servo track, and one
of the second cyclical patterns overlaps at least part of the first servo
track. At least one of the first and second set of time-based servo
patterns are demodulated by detecting first and second time intervals
relative to the timing marks, and a control signal for actuating the head
is generated in response to the first and second time intervals.