Method for data recovery on a data carrier with overlapping data tracks and device thereof

• US 20150254144A1
• Filed: 03/02/2015
• Published: 09/10/2015
• Est. Priority Date: 03/04/2014
• Status: Active Grant

• Current Assignee: Inodyn Newmedia GmbH
• Original Assignee: Inodyn Newmedia GmbH
• Inventors: Pantel, Lothar
• Granted Patent: US 9,336,096 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G06F 12/10 Address translation
• CPC Class Codes: G06F 2212/1032 Reliability improvement, data loss prevention, degraded operation etc
• CPC Class Codes: G06F 2212/152 Virtualized environment, e.g. logically partitioned system
• CPC Class Codes: G06F 2212/21 Employing a record carrier using a specific recording technology
• CPC Class Codes: G06F 2212/657 Virtual address space management
• CPC Class Codes: G06F 2212/70 Details relating to dynamic memory management
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0673 Single storage device
• CPC Class Codes: G06F 3/0676 Magnetic disk device
• CPC Class Codes: G11B 20/1217 on discs
• CPC Class Codes: G11B 20/1252 for discontinuous data, e.g. digital information signals, computer programme data
• CPC Class Codes: G11B 2020/1238 track, i.e. the entire a spirally or concentrically arranged path on which the recording marks are located

Abstract

A defect management system for storage devices is disclosed, which may be used in connection with shingled magnetic recording (SMR). Overlapping data tracks, separated by guard regions, are written by a write element whose track width is at least twice as wide as the track width of a read element. Depending on the embodiment, data recovery of a defective track or sector is attained by evaluating the contents of an adjacent track or guard region: if the adjacent track or guard region encompasses equivalent data, due to the width of the write element, this data may be used as a complement or as a substitute for the defective track or sector. This may reduce the risk of data loss. The capacity of a storage device may be increased by balancing out the probability of read errors with the probability that an adjacent track may encompass equivalent data.

Claims

1. A method for data recovery on a data carrier surface, comprising:

a) writing at least two overlapping data tracks by means of a write element whose data track width is at least twice as wide as the track width of a read element,

b) reading the data of at least a section of a source track by means of said read element,

c) evaluating by means of error control the accuracy of said data, and in the event that said data are inaccurate;

d) determining by means of management data and/or similarity comparison whether a corresponding section on an adjacent track and/or on a track in the vicinity of said source track encompasses equivalent data by virtue of the width of said write element, and if this is the case;

e) using at least a part of the data stored on said corresponding section complementarily or as a substitute for inaccurate data derived from said source track.

2. The method of claim 1, further comprising groups of tracks separated by guard regions, wherein in the event of a read error it is checked by means of management data whether the track adjacent to said source track is a guard region, and if this is the case, the data from said guard region are read at least from a corresponding section, such that the data can be used as a complement or as a substitute for inaccurate data derived from said source track.

3. The method of claim 1, further comprising writing a data track on at least two adjacent tracks in a single pass by means of said write element and storing management data containing the information that said adjacent tracks temporarily encompass equivalent data at least on a section.

4. The method of claim 3, further comprising:

a) reading data from the first track of said adjacent tracks by means of said read element and in the event of a read error;

b) determining by means of the information contained in said management data whether the second track of said adjacent tracks still encompasses equivalent data, and if this is the case;

c) reading data from said second track and using at least a portion as a complement or as a substitute for the inaccurate data derived from said first track.

5. The method of claim 1, further comprising:

a) writing a data track on at least two adjacent tracks in a single pass by means of said write element,

b) reading data from the first track of said adjacent tracks by means of said read element, and in the event of a read error;

c) reading data at least from a second track adjacent to said first track,

d) comparing the inaccurate data derived from said first track with the data derived from said second track by means of a decision criterion, and if the data are sufficiently equal;

e) using at least a part of the data derived from said second track as a complement or as a substitute for the inaccurate data derived from said first track.

6. The method of claim 5, further comprising reading data from at least one track in the vicinity of said first track and using at least a portion of the data as a complement or as a substitute if the data are sufficiently equal to the inaccurate data derived from said first track.

7. The method of claim 1, further comprising increasing the capacity of said data carrier surface by balancing out the probability of read errors with the probability that a track or guard region in the vicinity of a defective track encompasses, at least partly, equivalent data.

8. The method of claim 1, further comprising at least one band whose associated guard region is located in the middle or near the middle of said band, both tracks adjacent to said guard region being written such that the data track width of said write element is caught by said guard region from both sides.

9. The method of claim 8, wherein overlapping data tracks, written by said write element, converge from both outer boundaries of said band inwards, toward said guard region, establishing overlaps in opposite radial directions within said band.

10. The method of claim 8, further comprising:

a) displacing said guard region onto the physical location of a defective section,

b) adjusting the order and overlaps of the data tracks within said band such that the new physical location of said guard region is used,

c) storing data at least on the former physical location of said guard region.

11. The method of claim 1, wherein:

a) said data carrier surface is a disk surface of a hard disk drive that operates according to the shingled magnetic recording methodology,

b) said overlapping data tracks are grouped into bands and are separated by guard regions in accordance with the shingled magnetic recording methodology,

c) sections of a track are physical sectors,

d) said management data are processed by a hard disk controller of said hard disk drive.

12. A storage device configured for overlapping data tracks, comprising:

a) at least one data carrier surface,

b) a write element whose data track width is at least twice as wide as the track width of a read element,

c) at least two overlapping data tracks written on said data carrier surface by means of said write element,

d) a control unit configured to read the data of at least a section of a source track by means of said read element, wherein the accuracy of said data is evaluated by means of error control, and for the situation that said data are inaccurate, said control unit is configured to determine by means of management data and/or similarity comparison whether a corresponding section on an adjacent track and/or on a track in the vicinity of said source track encompasses equivalent data by virtue of the width of said write element, and for the situation that this proves true, said control unit is configured to use at least a part of the data stored on said corresponding section as a complement or as a substitute for inaccurate data derived from said source track.

13. The storage device of claim 12, further comprising groups of tracks separated by guard regions, wherein said control unit is configured to check, in the event of a read error, whether the track adjacent to said source track is a guard region, and if this is the case, said control unit is configured to read data from said guard region at least from a corresponding section, such that the data can be used as a complement or as a substitute for inaccurate data derived from said source track.

14. The storage device of claim 12, wherein the capacity of said data carrier surface is increased such that an increased probability of read errors is balanced out with the probability that a track or guard region in the vicinity of a defective track encompasses, at least partly, equivalent data.

15. The storage device of claim 12, further comprising at least one band whose associated guard region is located in the middle or near the middle of said band, wherein the width of data tracks, written on both tracks adjacent to said guard region, is caught by said guard region from both sides.

16. The storage device of claim 15, wherein overlapping data tracks converge from both outer boundaries of said band inwards, toward said guard region, establishing overlaps in opposite radial directions within said band.

17. The storage device of claim 12, wherein:

a) said storage device is a hard disk drive that operates according to the shingled magnetic recording methodology,

b) said data carrier surface is a disk surface of said hard disk drive,

c) said overlapping data tracks are grouped into bands and are separated by guard regions in accordance with the shingled magnetic recording methodology,

d) sections of a track are physical sectors,

e) said control unit is a hard disk controller of said hard disk drive.

18. A hard disk controller comprising control circuitry configured to:

a) write at least two overlapping data tracks by means of a write element whose data track width is at least twice as wide as the track width of a read element,

b) read the data of at least a section of a source track by means of said read element,

c) evaluate by means of error control the accuracy of said data, and for the situation that said data are inaccurate, said control circuitry is configured to;

d) determine by means of management data and/or similarity comparison whether a corresponding section on an adjacent track and/or on a track in the vicinity of said source track encompasses equivalent data by virtue of the width of said write element, and for the situation that this proves true, said control circuitry is configured to;

e) use at least a part of the data stored on said corresponding section as a complement or as a substitute for inaccurate data derived from said source track.