Disk drive self servo writing spiral tracks by propagating bursts

1. A disk drive comprising:

a disk;

a head actuated over the disk; and

control circuitry operable to:

(a) position the head at a radial location over the disk;

(b) write a servo burst at the current radial location;

(c) read the servo burst to generate a read signal;

(d) process the read signal to generate a position error signal (PES);

(e) move the head radially in response to the PES; and

(f) repeat (b) through (e) multiple times to form a spiral track spanning at least one revolution of the disk in a circumferential direction, and scanning a substantial part of the disk in a radial direction;

wherein:

the head comprises a read element radially offset from the write element; and

the control circuitry is further operable to write a seed track to the disk by:

positioning the write element at first radial location;

writing a first servo burst at the first radial location;

positioning the read element at a first percentage over the first servo burst in order to position the write element at a second radial location;

writing a second servo burst at the second radial location;

positioning the read element at a second percentage over the first servo burst in order to position the write element at a third radial location;

writing a third servo burst at the third radial location; and

the head is positioned at the radial location over the disk in step (a) in response to the seed track.

2. The disk drive as recited in claim 1 , wherein:

the head comprises a read element offset radially from a write element; and

the write element leads the read element as the head moves radially over substantially the entire radius of the disk.

3. The disk drive as recited in claim 1 , wherein the spiral track spans multiple revolutions of the disk.

4. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to repeat (a) through (f) to write a plurality of spiral tracks to the disk.

5. The disk drive as recited in claim 1 , wherein each servo burst comprises a high frequency signal interrupted by a sync mark at a sync mark interval.

6. The disk drive as recited in claim 1 , wherein the control circuitry is operable to move the head radially at (e) from an outer diameter of the disk toward an inner diameter of the disk.

7. The disk drive as recited in claim 1 , wherein the control circuitry is operable to move the head radially at (e) from an inner diameter of the disk toward an outer diameter of the disk.

8. The disk drive as recited in claim 1 , wherein the control circuitry is operable to generate the PES relative to an amplitude of the read signal.

9. The disk drive as recited in claim 1 , wherein the control circuitry is operable to read at least two of the servo bursts to generate the read signal used to generate the PES.

10. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to process the spiral track to write concentric servo sectors to the disk.

11. The disk drive as recited in claim 1 , wherein:

the first percentage is approximately twenty-five percent; and

the second percentage is approximately seventy-five percent.

12. A method of writing a spiral track to a disk of a disk drive, the disk drive comprising a head actuated over the disk, the method comprising:

(a) positioning the head at a radial location over the disk;

(b) writing a servo burst at the current radial location;

(c) reading the servo burst to generate a read signal;

(d) processing the read signal to generate a position error signal (PES);

(e) moving the head radially in response to the PES; and

(f) repeating (b) through (e) multiple times to form a spiral track spanning at least one revolution of the disk in a circumferential direction, and scanning a substantial part of the disk in a radial direction;

wherein:

the head comprises a read element radially offset from the write element; and

the method further comprises writing a seed track to the disk by:

positioning the write element at first radial location;

writing a first servo burst at the first radial location;

positioning the read element at a first percentage over the first servo burst in order to position the write element at a second radial location;

writing a second servo burst at the second radial location;

positioning the read element at a second percentage over the first servo burst in order to position the write element at a third radial location;

writing a third servo burst at the third radial location; and

the head is positioned at the radial location over the disk in step (a) in response to the seed track.

13. The method as recited in claim 12 , wherein:

the head comprises a read element offset radially from a write element; and

the write element leads the read element as the head moves radially over substantially the entire radius of the disk.

14. The method as recited in claim 12 , wherein the spiral track spans multiple revolutions of the disk.

15. The method as recited in claim 12 , further comprising repeating (a) through (f) to write a plurality of spiral tracks to the disk.

16. The method as recited in claim 12 , wherein each servo burst comprises a high frequency signal interrupted by a sync mark at a sync mark interval.

17. The method as recited in claim 12 , wherein moving the head radially at (e) comprises moving the head from an outer diameter of the disk toward an inner diameter of the disk.

18. The method as recited in claim 12 , wherein moving the head radially at (e) comprises moving the head from an inner diameter of the disk toward an outer diameter of the disk.

19. The method as recited in claim 12 , wherein the PES is generated relative to an amplitude of the read signal.

20. The method as recited in claim 12 , further comprising reading at least two of the servo bursts to generate the read signal used to generate the PES.

21. The method as recited in claim 12 , further comprising processing the spiral track to write concentric servo sectors to the disk.

22. The method as recited in claim 12 , wherein:

the first percentage is approximately twenty-five percent; and

the second percentage is approximately seventy-five percent.