An apparatus, system, and method are disclosed for variable data density
patterned media. The apparatus includes a patterned media recording
surface comprising a plurality of sectors. Each sector may include a
synchronization region configured to generate a signal in a read head, a
first data region with a first data density configured to generate a
signal with a first frequency, and at least a second data region with a
second data density configured to generate a signal with a second
frequency. The system includes a hard disk drive and the apparatus. The
method includes sensing a signal in a read head, synchronizing the
frequency and phase of a write clock with a predetermined frequency and
phase of a synchronization region, and modifying the frequency of the
write clock after a period of time determined in response to at least one
physical characteristic of the disk.