Patent ID: 8593748

Claim:
A shingled magnetic recording disk drive comprising: a magnetic recording disk having a recording surface with a plurality of concentric shingled data tracks arranged in annular bands separated by annular inter-band gaps, each band having a boundary region of tracks adjacent a gap, whereby each gap is located between adjacent boundary regions, the recording surface also having an extended cache region comprising a plurality of concentric data tracks separated from the data bands; a write head associated with said disk surface for generating a magnetic write field to write data to the tracks; a read head for reading data written in the tracks; a controller for controlling the writing of data by the write head to the tracks; and memory coupled to the controller and containing a program of instructions readable by the controller for minimizing the effect of encroachment of the write field on tracks in a band when data is being written outside the band, the program of instructions undertaking the method acts comprising: (a) maintaining in memory a count for each band; (b) for each writing of data to a band, incrementing the count for that band; and (c) when a count reaches a predetermined threshold for a band, reading the data from the tracks in the boundary region of an adjacent band; (d) writing the data read from the tracks in the boundary region of said adjacent band to the extended cache region; and (e) invalidating the tracks in the boundary region of said adjacent band from which the data was read.