Shingled magnetic recording storage system
The disclosed technology includes 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 (PES 1 ) when an off-track write operation occurs, determining whether the PES 1 meets a first pre-determined threshold, continue writing data to a second track responsive to determining the PES 1 is below a first pre-determined threshold, calculating a percentage of PES at a shingled side end of the second track (PES 2 ), determining whether a combined value of PES 1 and PES 2 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 (PES 1 );
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:
determining which side of the band is a shingled side; and
calculating the PES 1 at a shingled side end of the initial track when an off-track write operation occurs.
3. 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.
4. 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.
5. 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.
6. The method of claim 5 , 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.
7. The method of claim 5 , 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.
8. 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 (PES 1 ); 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 system of claim 8 , wherein the PES module is configured to calculate the PES 1 at a shingled side end of the initial track when an off-track write operation occurs.
10. The system of claim 8 , wherein the storage controller is further configured to:
re-write data to a media cache responsive to determining the PES 1 is above the first pre-determined threshold.
11. The system of claim 8 , wherein the storage controller is further configured to:
re-write data to the initial track responsive to determining the PES 1 is above the first pre-determined threshold.
12. The 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.
13. The system of claim 12 , wherein the storage controller is further configured to:
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.
14. The system of claim 13 , wherein the storage controller is further configured to:
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.
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;
calculating a percentage of position error signal (PES) of the initial track (PES 1 );
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 , the computer process further comprising:
determining which side of the initial track is a shingled side; and
calculating a PES 1 at a shingled side end of the initial track when an off-track write operation occurs.
17. The one or more tangible computer-readable storage media of claim 15 , the computer process further comprising:
re-writing data to media cache 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 , the computer process further comprising:
re-writing data to the initial track responsive to determining the PES 1 is above the first pre-determined threshold.
19. The one or more tangible computer-readable storage media of claim 15 , the computer process 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.
20. The one or more tangible computer-readable storage media of claim 19 , the computer process 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.