Method of accessing variable density data tracks in a disk drive

1. In a disk drive that includes first and second disk surfaces and first and second heads, wherein the first disk surface includes a first region, the second disk surface includes a second region, the first region includes first data tracks and first servo tracks, the second region includes second data tracks and second servo tracks, the first data tracks have a first radial data track density, the second data tracks have a second radial data track density, the first radial data track density is different than the second radial data track density, the first and second regions are radially similarly situated at essentially the same radial locations, the first head reads from and writes to the first disk surface, and the second head reads from and writes to the second disk surface, a method of sequentially accessing data in the first and second regions, comprising: sequentially accessing multiple first data tracks; and then sequentially accessing multiple second data tracks, wherein the multiple first data tracks are a subset of the first data tracks, the multiple second data tracks are a subset of the second data tracks, and the subsets of the first and second data tracks are radially similarly situated at essentially the same radial locations.

2. The method of claim 1 , wherein the first and second disk surfaces are opposite surfaces on a disk.

3. The method of claim 1 , wherein the first and second regions have inner boundaries at the same radial location, and the first and second regions have outer boundaries at the same radial location.

4. The method of claim 1 , wherein the first and second regions have the same linear bit density.

5. The method of claim 1 , wherein the first and second regions have different linear bit density.

6. The method of claim 1 , wherein the first head has a first measured performance in the first region, the second head has a second measured performance in the second region, and the first measured performance is different than the second measured performance.

7. The method of claim 6 , wherein the first and second measured performances include squeezed and unsqueezed off-track capability.

8. The method of claim 1 , wherein the multiple first data tracks are the first data tracks, and the multiple second data tracks are the second data tracks.

9. The method of claim 1 , including sequentially accessing the multiple first data tracks in a radial direction, and then sequentially accessing the multiple second data tracks in the radial direction.

10. The method of claim 1 , including sequentially accessing the multiple first data tracks in a first radial direction, and then sequentially accessing the multiple second data tracks in a second radial direction opposite the first radial direction.

11. The method of claim 1 , including performing a seek operation between sequentially accessing the multiple first data tracks and sequentially accessing the multiple second data tracks.

12. The method of claim 1 , excluding performing a seek operation between sequentially accessing the multiple first data tracks and sequentially accessing the multiple second data tracks.

13. The method of claim 1 , including sequentially accessing the multiple first data tracks in a first radial direction, then performing a head switch from the first head to the second head and a seek operation in a second radial direction opposite the first radial direction, and then sequentially accessing the multiple second data tracks in the first radial direction.

14. The method of claim 1 , including sequentially accessing the multiple first data tracks in a first radial direction, then performing a head switch from the first head to the second head without a seek operation, and then sequentially accessing the multiple second data tracks in a second radial direction opposite the first radial direction.

15. The method of claim 1 , including sequentially accessing the data in the first and second regions during a read operation.

16. The method of claim 1 , including sequentially accessing the data in the first and second regions during a write operation.

17. In a disk drive that includes first and second disk surfaces and first and second heads, wherein the first disk surface includes a first region, the second disk surface includes a second region, the first region includes first data tracks and first servo tracks, the second region includes second data tracks and second servo tracks, the first data tracks have a first radial data track density, the second data tracks have a second radial data track density, the first radial data track density is different than the second radial data track density, the first and second regions are radially similarly situated at essentially the same radial locations, the first head reads from and writes to the first disk surface, and the second head reads from and writes to the second disk surface, a method of sequentially accessing data in the first and second regions, comprising: sequentially accessing multiple first data tracks: and then sequentially accessing multiple second data tracks, wherein the first and second servo tracks have the same servo radial track density, wherein the servo radial track density of the first and second servo tracks is greater than the first and second radial data track densities.

18. In a disk drive that includes first and second disk surfaces and first and second heads, wherein the first disk surface includes a first region, the second disk surface includes a second region, the first region includes first data tracks and first servo tracks, the second region includes second data tracks and second servo tracks, the first data tracks include first initial and first last data tracks and have a first data track density, the second data tracks include second initial and second last data tracks and have a second data track density, the first data track density is different than the second data track density, the first and second regions are radially similarly situated at essentially the same radial locations, the first and second initial data tracks are radially similarly situated at essentially the same radial locations, the first and second last data tracks are radially similarly situated at essentially the same radial locations, the first head reads from and writes to the first disk surface, and the second head reads from and writes to the second disk surface, a method of sequentially accessing data in the first and second regions, comprising:

sequentially accessing the first data tracks starting with the first initial data track and ending with the first last data track using the first head and seek operations to move the first head in a first radial direction between adjacent first data tracks; then

performing a head switch from the first head to the second head and a seek operation in a second radial direction opposite the first radial direction to move the second head to the second initial data track; and then

sequentially accessing the second data tracks starting with the second initial data track and ending with the second last data track using the second head and seek operations to move the second head in the first radial direction between adjacent second data tracks.

19. The method of claim 18 , wherein the first and second disk surfaces are opposite surfaces on a disk.

20. The method of claim 18 , wherein the first and second regions have inner boundaries at the same radial location, and the first and second regions have outer boundaries at the same radial location.

21. The method of claim 18 , wherein the first and second regions have the same linear bit density.

22. The method of claim 18 , wherein the first and second regions have different linear bit density.

23. The method of claim 18 , wherein the first and second servo tracks have the same servo track density.

24. The method of claim 23 , wherein the servo track density is greater than the first and second data track densities.

25. The method of claim 18 , wherein the first and second data track densities are constant.

26. The method of claim 18 , wherein the first head has a first measured performance in the first region, the second head has a second measured performance in the second region, and the first measured performance is different than the second measured performance.

27. The method of claim 26 , wherein the first and second measured performances include squeezed and unsqueezed off-track capability.

28. In a disk drive that includes first and second disk surfaces and first and second heads, wherein the first disk surface includes a first region, the second disk surface includes a second region, the first region includes first data tracks and first servo tracks, the second region includes second data tracks and second servo tracks, the first data tracks include first initial and first last data tracks and have a first data track density, the second data tracks include second initial and second last data tracks and have a second data track density, the first data track density is different than the second data track density, the first and second regions are radially similarly situated at essentially the same radial locations, the first and second initial data tracks are radially similarly situated at essentially the same radial locations, the first and second last data tracks are radially similarly situated at essentially the same radial locations, the first head reads from and writes to the first disk surface, and the second head reads from and writes to the second disk surface, a method of sequentially accessing data in the first and second regions, comprising:

sequentially accessing the first data tracks starting with the first initial data track and ending with the first last data track using the first head and seek operations to move the first head in a first radial direction between adjacent first data tracks; then

performing a head switch from the first head to the second head without a seek operation; and then

sequentially accessing the second data tracks starting with the second last data track and ending with the second initial data track using the second head and seek operations to move the second head in a second radial direction opposite the first radial direction between adjacent second data tracks.

29. The method of claim 28 , wherein the first and second disk surfaces are opposite surfaces on a disk.

30. The method of claim 28 , wherein the first and second regions have inner boundaries at the same radial location, and the first and second regions have outer boundaries at the same radial location.

31. The method of claim 28 , wherein the first and second regions have the same linear bit density.

32. The method of claim 28 , wherein the first and second regions have different linear bit density.

33. The method of claim 28 , wherein the first and second servo tracks have the same servo track density.

34. The method of claim 33 , wherein the servo track density is greater than the first and second data track densities.

35. The method of claim 28 , wherein the first and second data track densities are constant.

36. The method of claim 28 , wherein the first head has a first measured performance in the first region, the second head has a second measured performance in the second region, and the first measured performance is different than the second measured performance.

37. The method of claim 36 , wherein the first and second measured performances include squeezed and unsqueezed off-track capability.

38. In a disk drive that includes first and second disk surfaces and first and second heads, wherein the first disk surface includes a first region, the second disk surface includes a second region, the first region includes, first data tracks and first servo tracks, the second region includes second data tracks and second servo tracks, the first data tracks include first initial, first intermediate and first last data tracks and have a first data track density, the second data tracks include second initial, second intermediate and second last data tracks and have a second data track density, the first data track density is different than the second data track density, the first and second regions are radially similarly situated at essentially the same radial locations, the first and second initial data tracks are radially similarly situated at essentially the same radial locations, the first and second intermediate data tracks are radially similarly situated at essentially the same radial locations, the first and second last data tracks are radially similarly situated at essentially the same radial locations, the first head reads from and writes to the first disk surface, and the second head reads from and writes to the second disk surface, a method of sequentially accessing data in the first and second regions, comprising:

sequentially accessing a first subset of the first data tracks starting with the first initial data track and ending with the first intermediate data track using the first head and seek operations to move the first head in a first radial direction between adjacent first data tracks; then

performing a head switch from the first head to the second head without a seek operation; then

sequentially accessing a first subset of the second data tracks starting with the second intermediate data track and ending with the second initial data track using the second head and seek operations to move the second head in a second radial direction opposite the first radial direction between adjacent second data tracks; then

performing a head switch from the second head to the first head and a seek operation in the first radial direction to move the first head to another first data track between the first intermediate and the first last data track and adjacent to the first intermediate data track; then

sequentially accessing a second subset of the first data tracks starting with the another first data track using the first head and seek operations to move the first head in the first radial direction between adjacent first data tracks; then

performing a head switch from the first head to the second head without a seek operation; and then

sequentially accessing a second subset of the second data tracks starting with another second data track between the second intermediate and the second last data track and adjacent to the second intermediate data track using the second head and seek operations to move the second head in the second radial direction between adjacent second data tracks.

39. The method of claim 38 , wherein the first and second disk surfaces are opposite surfaces on a disk.

40. The method of claim 38 , wherein the first and second regions have inner boundaries at the same radial location, and the first and second regions have outer boundaries at the same radial location.

41. The method of claim 38 , wherein the first and second regions have the same linear bit density.

42. The method of claim 38 , wherein the first and second regions have different linear bit density.

43. The method of claim 38 , wherein the first and second servo tracks have the same servo track density.

44. The method of claim 43 , wherein the servo track density is greater than the first and second data track densities.

45. The method of claim 38 , wherein the first and second data track densities are constant.

46. The method of claim 38 , wherein the first head has a first measured performance in the first region, the second head has a second measured performance in the second region, and the first measured performance is different than the second measured performance.

47. The method of claim 46 , wherein the first and second measured performances include squeezed and unsqueezed off-track capability.