Disk drive with variable incremented counting of writes to the data tracks for minimizing the effect of far track erasure
A hard disk drive (HDD) minimizes the effects of far track erasure (FTE) by counting the number of writes to the data tracks and incrementing counters based on the known effect of FTE on each track. The extent of the FTE effect is determined for each track within a range of tracks of the track being written, and based on the relative FTE effect for all the tracks in the range a count increment (CI) is determined for each track within the range. A counter is maintained for each track. For every writing to a track, a count for each track within a range of the track being written is increased by the CI value associated with the track number within the range. When the count value for a track reaches a predetermined threshold the data is read from that track and rewritten, preferably to the same track.
1. A magnetic recording disk drive comprising:
a magnetic recording disk having a plurality of concentric data tracks on a surface of the disk for the storage of data;
a write head associated with said disk surface for generating a magnetic write field to write data to the data tracks;
a read head for reading data written in the data tracks;
a controller for controlling the writing of data by the write head to the data 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 data tracks within a range between −N tracks and +N tracks of the data track being written, the program of instructions undertaking the method acts comprising:
(a) maintaining in memory a count for each track, the memory including a table of 2N tracks having range numbers between −N and +N and corresponding 2N increment values;
(b) for each writing of data to a track, determining the range number for each track within said range, recalling from the table in memory the corresponding increment value and increasing said count by said recalled increment value for each track within said range; and
(c) when a count for a track reaches a predetermined threshold, reading the data from said threshold-count track and rewriting the data read from said threshold-count track.
2. The disk drive of claim 1 wherein each of the 2N increment values is related to a measured error rate for the corresponding track.
3. The disk drive of claim 1 wherein the disk surface has a plurality of annular zones, each having a plurality of concentric data tracks, and wherein the program of instructions comprise undertaking method acts (a) through (c) for each zone.
4. The disk drive of claim 1 wherein the disk drive has a plurality of disk surfaces, each having a plurality of concentric data tracks, and associated write heads, and wherein the program of instructions comprise undertaking method acts (a) through (c) for each disk surface.
5. The disk drive of claim 1 wherein the write head is a perpendicular write head.
6. The disk drive of claim 1 wherein the memory is nonvolatile memory.
7. A magnetic recording disk drive comprising:
a magnetic recording disk having a plurality of concentric data tracks on a surface of the disk for the storage of data;
a write head associated with said disk surface for generating a magnetic write field to write data to the data tracks;
a read head for reading data written in the data tracks;
a controller for controlling the writing of data by the write head to the data tracks; and
memory coupled to the controller, the memory containing a table of multiple-track data segments and corresponding count increment values and a program of instructions readable by the controller for minimizing the effect of encroachment of the write field on segments within a predetermined range of the segment in which a data track is being written, the program of instructions undertaking the method acts comprising:
(a) maintaining in memory a count for each segment;
(b) for each writing of data to a track, recalling from the table in memory the corresponding count increment value for each segment within the range and increasing said count for each segment within the range by said recalled count increment value; and
(c) when a count for a segment reaches a predetermined threshold, reading the data from all of the tracks in said threshold-count segment and rewriting the data read from said threshold-count segment.
8. The disk drive of claim 7 wherein there are M data tracks in each segment and further comprising M tables of multiple-track data segments and corresponding count increment values in memory, and wherein recalling from the table in memory comprises first selecting one of the M tables in response to which of the 0 to M−1 tracks is being written in the segment being written.
9. The disk drive of claim 7 wherein M equals 4.
10. The disk drive of claim 7 wherein each of the count increment values is related to the sum of the measured error rates for all the tracks in the corresponding segment.
11. The disk drive of claim 7 wherein the disk surface has a plurality of annular zones, each having a plurality of concentric data tracks, and wherein the program of instructions comprise undertaking method acts (a) through (c) for each zone.
12. The disk drive of claim 7 wherein the disk drive has a plurality of disk surfaces, each having a plurality of concentric data tracks, and associated write heads, and wherein the program of instructions comprise undertaking method acts (a) through (c) for each disk surface.
13. The disk drive of claim 7 wherein the write head is a perpendicular write head.
14. The disk drive of claim 7 wherein the memory is nonvolatile memory.