Compensation for nonlinearity in servo patterns

1. A method, comprising:

generating a y-position estimate based on a servo readback signal from a servo reader reading a servo band;

retrieving or calculating a nonlinearity-correction value corresponding to the y-position estimate;

adjusting the y-position estimate using the nonlinearity-correction value; and

outputting the adjusted y-position estimate.

2. The method as recited in claim 1 , wherein the nonlinearity-correction value is retrieved from a table.

3. The method as recited in claim 2 , wherein the table includes a plurality of nonlinearity-correction values corresponding to known locations relative to the servo band.

4. The method as recited in claim 1 , wherein the nonlinearity-correction value is retrieved from a source selected from the group consisting of: a magnetic tape cartridge memory, data stored on a magnetic tape, and a magnetic tape library memory.

5. The method as recited in claim 1 , wherein the nonlinearity-correction value corresponding to the y-position estimate is calculated by interpolation of nonlinearity-correction values corresponding to known locations in a vicinity of the estimated y-position.

6. The method as recited in claim 1 , wherein the nonlinearity-correction value is calculated using a function for directly computing the nonlinearity-correction value as a function of the y-position estimate.

7. The method as recited in claim 1 , comprising:

generating a second y-position estimate based on a second servo readback signal from a second servo reader reading a second servo band;

retrieving or calculating a second nonlinearity-correction value corresponding to the second y-position estimate;

adjusting the second y-position estimate using the nonlinearity-correction value;

outputting the adjusted second y-position estimate; and

combining the adjusted y-position estimate and the adjusted second y-position estimate.

8. The method as recited in claim 7 , wherein the nonlinearity-correction value is calculated using a function for directly computing the nonlinearity-correction value as a function of the y-position estimate, wherein the second nonlinearity-correction value is calculated using a second function for directly computing the nonlinearity-correction value as a function of the second y-position estimate, wherein the function and second functions are different.

9. The method as recited in claim 1 , comprising: using the adjusted y-position estimate for adjusting a head position of a magnetic tape head thereafter reading the servo band.

10. A computer program product for compensating for nonlinearity in a timing based servo pattern, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, wherein the computer readable storage medium is not a transitory signal per se, the program instructions readable and/or executable by a controller to cause the controller to perform a method comprising:

generating, by the controller, a y-position estimate based on a servo readback signal from a servo reader reading a servo band;

retrieving or calculating, by the controller, a nonlinearity-correction value corresponding to the y-position estimate;

adjusting, by the controller, the y-position estimate using the nonlinearity-correction value; and

outputting, by the controller, the adjusted y-position estimate.

11. The computer program product as recited in claim 10 , wherein the nonlinearity-correction value is retrieved from a table.

12. The computer program product as recited in claim 11 , wherein the table includes a plurality of nonlinearity-correction values corresponding to known locations relative to the servo band.

13. The computer program product as recited in claim 10 , wherein the nonlinearity-correction value is retrieved from a source selected from the group consisting of: a magnetic tape cartridge memory, data stored on a magnetic tape, and a magnetic tape library memory.

14. The computer program product as recited in claim 10 , wherein the nonlinearity-correction value is calculated by interpolation using nonlinearity-correction values corresponding to known locations relative to the servo band.

15. The computer program product as recited in claim 10 , wherein the nonlinearity-correction value is calculated using a function for directly computing the nonlinearity-correction value as a function of the y-position estimate.

16. The computer program product as recited in claim 10 ,

generating a second y-position estimate based on a second servo readback signal from a second servo reader reading a second servo band;

retrieving or calculating a second nonlinearity-correction value corresponding to the second y-position estimate;

adjusting the second y-position estimate using the nonlinearity-correction value;

outputting the adjusted second y-position estimate; and

combining the adjusted y-position estimate and the adjusted second y-position estimate.

17. The computer program product as recited in claim 16 , wherein the nonlinearity-correction value is calculated using a function for directly computing the nonlinearity-correction value as a function of the y-position estimate, wherein the second nonlinearity-correction value is calculated using a second function for directly computing the nonlinearity-correction value as a function of the second y-position estimate, wherein the function and second functions are different.

18. The computer program product as recited in claim 10 , comprising: using the adjusted y-position estimate for adjusting a head position of a magnetic tape head thereafter reading the servo band.

19. An apparatus, comprising:

a controller configured to:

generate a y-position estimate based on a servo readback signal from a servo reader reading a servo band;

retrieve or calculate a nonlinearity-correction value corresponding to the y-position estimate;

adjust the y-position estimate using the nonlinearity-correction value; and

output the adjusted y-position estimate.

20. The apparatus as recited in claim 19 , wherein the nonlinearity-correction value is calculated by interpolation using nonlinearity-correction values corresponding to known locations relative to the servo band.