Directional write retry for shingled disk drive application
View Patent ↗Embodiments described herein include systems and methods for correcting for errors caused by disturbances to disk drives, such as disturbances due to shocks or vibrations incident on the drive. For example, systems and methods described herein advantageously correct for corruption to current data as well as previously written. Data may be rewritten in the current track that was being written to when the disturbance occurred, and may also be rewritten to one or more nearby previously written tracks, such as one or more adjacent tracks. According to some aspects, the direction of head deviation is used to select the appropriate corrective action.
1. A method of performing error correction in a shingled disk drive, comprising:
writing data to a disk in a first radial direction using a head, the head moving according to a predetermined trajectory; and
by a controller of the disk drive:
receiving a signal indicating that the head has deviated from its predetermined trajectory while writing a current data sector to a first track of the disk;
in response to the signal, determining a direction in which the head deviated from the predetermined trajectory; and
when it is determined that the head deviated in the first radial direction, rewriting the current data sector to a second track located adjacent to the first track in the first radial direction; and
when it is determined that the head deviated in a second radial direction substantially opposite to the first radial direction:
rewriting one or more corrupted data sectors from a third track to the first track, the third track located adjacent to the first track in the second radial direction; and
rewriting one or more data sectors from the first track to the second track.
2. The method of claim 1 , wherein the writing comprises writing the data as a plurality of concentric tracks and wherein the tracks are written sequentially in the first radial direction.
3. The method of claim 2 , further comprising assessing the integrity of at least some of the data in one or more previously written tracks in order to identify the one or more corrupted data sectors from the third track.
4. The method of claim 2 , wherein when it is determined that the head deviated in the first radial direction, the current data sector is rewritten to the second track without assessing the integrity of data in any previously written tracks.
5. The method of claim 1 , wherein when it is determined that the head deviated in the first radial direction, the current data sector is rewritten to the second track without rewriting data from any previously written tracks.
6. The method of claim 1 , further comprising determining a maximum number of allowable adjacent track writes.
7. The method of claim 1 , further comprising:
storing data written to the one or more corrupted data sectors in a buffer; and
retrieving the data from the buffer for the rewriting of the one or more corrupted data sectors.
8. The method of claim 1 , further comprising determining a magnitude of head deviation, wherein determining that the head deviated in the first radial direction comprises determining that the magnitude of head deviation exceeds a first threshold value and determining that the head deviated in the second radial direction comprises determining that the magnitude of head deviation exceeds a second threshold value.
9. The method of claim 8 , wherein the first and second threshold values are write unsafe (WUS) limits and the first threshold value is greater than the second threshold value.
10. A shingled disk drive, comprising:
a rotatable disk;
a head configured to write data to the disk in a first radial direction and to move according to a predetermined trajectory; and
a controller configured to:
(a) receive a signal indicating that the head has deviated from its predetermined trajectory while writing a current data sector to a first track of the disk;
(b) determine, in response to the signal, a direction in which the head deviated from the predetermined trajectory;
(c) when it is determined that the head deviated in the first radial direction, rewriting the current data sector to a second track located adjacent to the first track in the first radial direction; and
(d) when it is determined that the head deviated in a second radial direction substantially opposite to the first radial direction:
rewriting one or more corrupted data sectors from a third track to the first track, the third track located adjacent to the first track in the second radial direction; and
rewriting one or more data sectors from the first track to the second track.
11. The shingled disk drive of claim 10 , wherein the head is configured to write data to the disk as a plurality of concentric tracks, wherein the tracks are written sequentially in the first radial direction.
12. The shingled disk drive of claim 11 , wherein the controller is further configured to access the integrity of at least some of the data in one or more previously written tracks in order to identify the one or more corrupted data sectors from the third track.
13. The shingled disk drive of claim 12 , wherein the controller is further configured to, when it is determined that the head deviated in the first radial direction, rewrite the current data sector to the sector without assessing the integrity of data in any previously written tracks.
14. The shingled disk drive of claim 10 , wherein the controller is further configured to, when it is determined that the head deviated in the first radial direction, rewrite the current data sector to the second track without rewriting data from any previously written tracks.
15. The shingled disk drive of claim 10 , wherein the controller is further configured to determine a maximum number of allowable adjacent track writes.
16. The shingled disk drive of claim 10 , further comprising:
a buffer configured to store data written to the one or more corrupted data sectors;
wherein the controller is further configured to retrieve the data from the buffer for rewriting of the one or more corrupted data sectors.
17. The shingled disk drive of claim 10 , wherein the signal comprises a position error signal (PES).
18. The shingled disk drive of claim 10 , further comprising a sensor configured to generate the signal.