Shingled magnetic recording storage system

1. A method comprising:

receiving a write command to write data on an initial track in a band of a shingled magnetic recording medium;

determining which side of the band is a shingled side;

calculating a percentage of position error signal (PES) at a shingled side end of the initial track (PES 1 ) when an off-track write operation occurs;

determining whether the percentage of PES 1 meets a first pre-determined threshold; and

writing data to a second track responsive to determining the percentage of PES 1 is below the first pre-determined threshold, the second track being adjacent to the first track in the shingled direction.

2. The method of claim 1 , further comprising:

re-writing data to a media cache responsive to determining the PES 1 is above the first pre-determined threshold.

3. The method of claim 1 , further comprising:

re-writing data to the initial track responsive to determining the PES 1 above the first pre-determined threshold.

4. The method of claim 1 , further comprising:

calculating a percentage of PES at a shingled side end of the second track (PES 2 ); and

determining whether a combined value of PES 1 and PES 2 is above a second pre-determined threshold to determine a probability value of the initial track being erased.

5. The method of claim 4 , further comprising:

re-writing data to the initial track responsive to determining a combined value of PES 1 and PES 2 is above a second pre-determined threshold.

6. The method of claim 4 , further comprising:

re-writing data to a media cache responsive to determining a combined value of PES 1 and PES 2 is above a second pre-determined threshold.

7. The method of claim 4 , further comprising:

writing data to a third track responsive to determining a combined value of PES 1 and PES 2 is below a second pre-determined threshold.

8. A storage device system, comprising:

a position error signal (PES) module configured to calculate a percentage of PES at a shingled side end of an initial track in a band in a shingled magnetic recording medium (PES 1 ) when an off-track write operation occurs; and

a storage controller configured to:

determine whether the PES 1 meets a first pre-determined threshold; and

write data to a second track responsive to determining the PES 1 is below the first pre-determined threshold, the second track being adjacent to the first track.

9. The storage device system of claim 8 , wherein the

re-write data to a media cache responsive to determining the PES 1 is above the first pre-determined threshold.

10. The storage device system of claim 8 , wherein the

re-write data to the initial track responsive to determining the PES 1 is above the first pre-determined threshold.

11. The storage device system of claim 8 , wherein the storage controller is further configured to:

calculate a percentage of PES at the second track (PES 2 ) at a shingled side end of the second track; and

determine whether a combined value of PES 1 and PES 2 is above a second pre-determined threshold to determine a probability value of the initial track being erased.

12. The storage device system of claim 11 , wherein the storage controller is further configured:

re-write data to media cache responsive to determining the combined value of PES 1 and PES 2 is above a second pre-determined threshold.

13. The storage device system of claim 12 , wherein the storage controller is further configured:

re-write data to the initial track responsive to determining the combined value of PES 1 and PES 2 is above a second pre-determined threshold.

14. The storage device system of claim 13 , wherein the storage controller is further configured to:

write to a third track responsive to determining the combined value of PES 1 and PES 2 is below a second pre-determined threshold.

15. One or more tangible computer-readable storage media encoding computer-executable instructions for executing on a computer system a computer process, the computer process comprising:

receiving a write command to write data on an initial track in a band of a shingled magnetic recording medium;

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 (PES 1 ) when an off-track write operation occurs;

determining whether the PES 1 meets a first pre-determined threshold; and

writing to a second track responsive to determining the PES 1 is below the first pre-determined threshold, the second track being adjacent to the first track.

16. The one or more tangible computer-readable storage media of claim 15 , further comprising:

re-writing data to media cache responsive to determining the PES 1 is above the first pre-determined threshold.

17. The one or more tangible computer-readable storage media of claim 15 , further comprising:

re-writing data to the initial track responsive to determining the PES 1 is above the first pre-determined threshold.

18. The one or more tangible computer-readable storage media of claim 15 , further comprising:

calculating a percentage of PES at the second track (PES 2 ) at a shingled side end of the second track; and

determining whether the PES 1 and the PES 2 are above a second pre-determined threshold to determine whether the initial track is erased.

19. The one or more tangible computer-readable storage media of claim 18 , further comprising:

re-writing data to the initial track responsive to determining the combined value of PES 1 and PES 2 is above a second pre-determined threshold.

20. The one or more tangible computer-readable storage media of claim 18 , further comprising:

writing data to a third track responsive to determining the combined value of PES 1 and PES 2 is below a second pre-determined threshold.