Shingled magnetic recording storage system
Methods and systems that reduce off-track write retry operations in shingled magnetic recording systems. In one implementation, the method includes writing data to an initial track, determining which side of the initial track is a shingled side, calculating a percentage of position error signal (PES) at a shingled side end of the initial track (PES1) when an off-track write operation occurs, determining whether the PES1 meets a first pre-determined threshold, continue writing data to a second track responsive to determining the PES1 is below a first pre-determined threshold, calculating a percentage of PES at a shingled side end of the second track (PES2), determining whether a combined value of PES1 and PES2 is above a second predetermined threshold to determine a probability value of the initial track being erased, and continue writing to a third track if the combined value is below the second predetermined threshold.
1. A method comprising:
receiving a write command to write data on an initial track in a band of a shingled magnetic recording medium;
calculating a percentage of position error signal (PES) of the initial track (PES1);
determining a relationship of the percentage of PES1 to a first pre-determined threshold;
responsive to the percentage of PES1 being above the first pre-determined threshold, re-writing the data to the initial track or to a media cache; and
responsive to the percentage of PES1 being below the first pre-determined threshold, writing the data to a second track adjacent the initial track.
2. The method of claim 1 , responsive to writing the data to the second track, further comprising:
calculating a percentage of PES of the second track (PES2); and
determining whether a combined value of percentage of PES1 and percentage of PES2 is above a second pre-determined threshold.
3. The method of claim 2 , further comprising:
re-writing the data to the initial track responsive to determining the combined value of percentage of PES1 and percentage of PES2 is above the second pre-determined threshold.
4. The method of claim 2 , further comprising:
re-writing the data to the media cache responsive to determining the combined value of percentage of PES1 and percentage of PES2 is above the second pre-determined threshold.
5. The method of claim 2 , further comprising:
writing new data to a third track responsive to determining the combined value of percentage of PES1 and percentage of PES2 is below the second pre-determined threshold.
6. The method of claim 1 , wherein responsive to the percentage of PES1 being above the first pre-determined threshold, re-writing the data to the initial track.
7. The method of claim 1 , wherein responsive to the percentage of PES1 being above the first pre-determined threshold, re-writing the data to the media cache.
8. The method of claim 1 , wherein the first pre-determined threshold is an off-track limit +2%, wherein the off-track limit is defined by an on-cylinder limit (OCLIM) for the initial track.
9. The method of claim 8 , wherein the first pre-determined threshold is 12%.
10. A system, comprising:
a position error signal (PES) module configured to calculate a percentage of PES of an initial track in a band in a shingled magnetic recording medium (PES1); and
a storage controller configured to:
determine whether the percentage of PES1 meets a first pre-determined threshold; and
responsive to determining the percentage of PES1 is above the first pre-determined threshold, re-write the data to the initial track or to a media cache; and
responsive to determining the percentage of PES1 is below the first pre-determined threshold, writing new data to a second track adjacent the initial track.
11. The system of claim 10 , wherein the storage controller is further configured to:
calculate a percentage of PES of the second track (PES2); and
determine whether a combined value of percentage of PES1 and percentage of PES2 is above a second pre-determined threshold.
12. The system of claim 11 , wherein the storage controller is further configured to:
re-write the data to the initial track responsive to determining the combined value of percentage of PES1 and percentage of PES2 is above the second pre-determined threshold.
13. The system of claim 11 , wherein the storage controller is further configured to:
re-write the data to the media cache responsive to determining the combined value of percentage of PES1 and percentage of PES2 is above the second pre-determined threshold.
14. The system of claim 11 , wherein the storage controller is further configured to:
write additional new data to a third track responsive to determining the combined value of percentage of PES1 and percentage of PES2 is below the second pre-determined threshold.
15. The system of claim 10 , wherein the storage controller is configured to:
re-write data to the media cache responsive to determining the percentage of PES1 is above the first pre-determined threshold.
16. The system of claim 10 , wherein the storage controller is configured to:
re-write data to the initial track responsive to determining the percentage of PES1 is above the first pre-determined threshold.
17. The system of claim 10 , wherein the first pre-determined threshold is an off-track limit +2%, wherein the off-track limit is defined by an on-cylinder limit (OCLIM) for the initial track.
18. The system of claim 17 , wherein the first pre-determined threshold is 12%.