Predictive characterization of adjacent track erasure in recording media
Cross-track density capability is predicted for a large number of writes based on a plurality of erase band width measurements. Over the plurality of erase band width measurements, a number of writes in a series of writes performed as part of an aggressing track sequence is varied. A model of the magnetic track width (MTW) as function of the number of writes employed in the MTW measurements may be generated and an estimate of the erase band width for a large number of writes derived from the model as a prediction of cross-track density capability.
1. A method for determining a cross-track density capability of a recording media, the method comprising:
squeezing a victim track with a first aggressing side track writing sequence until a signal stored on the victim track reaches a threshold level of degradation, the first aggressing side track writing sequence comprising:
iteratively displacing the side track in an across-track direction toward the victim track and performing a side track write n times with each iteration;
determining a first erase band width associated with the first aggressing side track writing sequence;
squeezing a victim track with a second aggressing side track writing sequence until a signal stored on the victim track reaches a threshold level of degradation, the second aggressing side track writing sequence comprising:
iteratively displacing the side track in an across-track direction toward the victim track and performing a side track write m times with each iteration, wherein m is different than n;
determining a second erase band width associated with the second aggressing side track writing sequence; and
generating, from the first and second erase band width, a model characterizing the erase band width of the media as a function of the number of side track writes in an aggressing side track writing sequence.
2. The method of claim 1 , further comprising generating from the model an estimate of the erase band width corresponding to a threshold number of side track writes greater than a sum of n and m.
3. The method of claim 2 , wherein generating the model further comprises:
determining a change of magnetic track width (MTW) as a function of the number of side track writes; and
wherein generating the estimate of the erase band width further comprises evaluating the MTW function at the threshold number of side track writes.
4. The method of claim 3 , wherein the change of MTW is modeled as a logarithmic function of the number of side track writes.
5. The method of claim 3 , wherein the n and m are both less than 100 and threshold number of side track writes is at least 5000.
6. The method as in claim 1 , wherein squeezing the victim track with the first and second aggressing side track writing sequences further comprises:
evaluating the detectable signal each time the number of side track writes are performed.
7. The method of claim 1 , further comprising squeezing a victim track with a third aggressing side track writing sequence by performing a side track write p times with each iteration, wherein p is different than m and n.
8. The method of claim 7 , wherein the numbers of side track writes in the series n, m, and p is incremented in a logarithmic progression.
9. The method of claim 1 , further comprising erasing the victim track between the first and second aggressing side track writing sequences.
10. A computer-accessible non-transitory storage medium with instructions stored thereon, which when executed by a computer system, cause the computer system to perform the method of claim 1 .
11. An automated tester for determining a cross-track density capability of a recording media, the automated tester comprising:
means for squeezing a victim track with a first aggressing side track writing sequence until a signal stored on the victim track reaches a threshold level of degradation, the first aggressing side track writing sequence comprising:
iteratively displacing the side track in an across-track direction toward the victim track and performing a side track write n times with each iteration;
means for determining a first erase band width associated with the first aggressing side track writing sequence;
means for squeezing a victim track with a second aggressing side track writing sequence until a signal stored on the victim track reaches a threshold level of degradation, the second aggressing side track writing sequence comprising:
iteratively displacing the side track in an across-track direction toward the victim track and performing a side track write m times with each iteration, wherein m is different than n;
means for determining a second erase band width associated with the second aggressing side track writing sequence; and
means for generating, from the first and second erase band width, a model characterizing the erase band width of the media as a function of the number of side track writes in an aggressing side track writing sequence.
12. The automated tester of claim 11 , further comprising:
means for generating from the model an estimate of the erase band width corresponding to a threshold number of side track writes greater than the sum of n and m.
13. The automated tester of claim 12 , wherein the model generating means further comprises:
means for determining a change of magnetic track width (MTW) as a function of the number of side track writes; and
wherein the estimating means further comprises a means for evaluating the MTW function at the threshold number of side track writes.
14. The automated tester of claim 13 , wherein the means for squeezing the victim track with the first and second aggressing side track writing sequences further comprises:
means for evaluating the detectable signal each time the number of side track writes are performed.
15. The automated tester of claim 11 , further comprising means for erasing the victim track between the first and second aggressing side track writing sequences.
16. An automated tester for determining a cross-track density capability of a recording media, the automated tester comprising:
a spinstand;
an MTW tester to squeeze a victim track with a first aggressing side track writing sequence until a signal stored on the victim track reaches a threshold level of degradation, the first aggressing side track writing sequence comprising:
iteratively displacing the side track in an across-track direction toward the victim track and performing a side track write n times with each iteration;
determine a first erase band width associated with the first aggressing side track writing sequence;
squeeze a victim track with a second aggressing side track writing sequence until a signal stored on the victim track reaches a threshold level of degradation, the second aggressing side track writing sequence comprising:
iteratively displacing the side track in an across-track direction toward the victim track and performing a side track write m times with each iteration, wherein m is different than n; and
determine a second erase band width associated with the second aggressing side track writing sequence; and
a MTW modeler to generate, from the first and second erase band width, a model characterizing the erase band width of the media as a function of the number of side track writes in an aggressing side track writing sequence.
17. The automated tester of claim 16 , further comprising:
an erase band width estimator to generate an estimate of the erase band width corresponding to a threshold number of side track writes.
18. The automated tester of claim 17 , wherein the modeler is to:
determine a change of a magnetic track width (MTW) as a function of the number of side track writes; and
wherein the erase band width estimator is to evaluate the MTW function at the threshold number of side track writes.
19. The automated tester of claim 16 , wherein the MTW tester is configured to erase the victim track between squeezing the victim track with the first and second aggressing side track writing sequences.