Hard disk drive fly height adjust method and apparatus during error recovery

• US 7,352,525 B1
• Filed: 06/07/2006
• Issued: 04/01/2008
• Est. Priority Date: 06/07/2005
• Status: Expired due to Fees

• Current Assignee: Maxtor Corporation (Seagate Technology Holdings Plc)
• Original Assignee: Maxtor Corporation (Seagate Technology Holdings Plc)
• Inventors: Moline, Jerry, Shrestha, Rajita, Green, Christine
• Primary Examiner(s): TZENG, FRED
• Application Number:
  US11/449,579
• Time in Patent Office: 664 Days
• Field of Search: 360/75, 360/31, 360/53, 360/25
• US Class Current: 360/75
• CPC Class Codes: G11B 19/041 Detection or prevention of read or write errors
• CPC Class Codes: G11B 5/6005 Specially adapted for spacing from a rotating disc using a fluid cushion
• CPC Class Codes: G11B 5/6029 Measurement using values derived from the data signal read from the disk
• CPC Class Codes: G11B 5/607 using thermal means

Abstract

Data recovery, following a read error in a hard disk drive, is provided which includes an adjustment of fly height. In one embodiment, some re-reads are performed by both adjusting the fly height and the off-track positioning of the read head. In one embodiment, two or more fly heights are normally used during read/write operations such as in a zoned manner, and adjustments to fly heights are performed with respect to the fly height for the zone where the error occurred.

Claims

1. An apparatus for use in a hard disk drive, having at least a first read head, which includes data written in a plurality of tracks having an average inter-track distance, comprising:

first circuitry which detects a read error at a first disk location while using a first normal fly height and outputs a first signal in response;

second circuitry which attempts at least a first re-read of data at said first disk location while positioning said read head so as to be both off-track by a first off-track amount less than said average inter-track distance and at a second fly height different from said first fly height and attempts an additional re-read of data at said first disk location while re-positioning said read head to be off-track by a second off-track amount different from said first off-track amount and at a fly height different from said first normal fly height.

2. An apparatus as claimed in claim 1, wherein said second circuitry positions said fly height to be different from said first normal fly height only after at least one attempt is made to re-read while said read head is at said first normal fly height.

3. An apparatus as claimed in claim 1, wherein said second fly height differs from said first normal fly height by an amount about equal to a multiple of 0.5 nm.

4. An apparatus as claimed in claim 1, wherein said second circuitry includes a programmed microcontroller.

5. An apparatus as claimed in claim 1, further comprising circuitry which attempts the additional re-read of data at said first disk location while positioning said read head so as to be at a fly height different from said second fly height and different from said first normal fly height.

6. A method for use in a hard disk drive, having at least a first read head, which includes data written in a plurality of tracks having an average inter-track distance, comprising:

detecting a read error at a first disk location while using a first normal fly height and outputting a first signal in response;

performing at least a first re-read of data at said first disk location while positioning said read head so as to be both off-track by a first off-track amount less than said average inter-track distance and at a second fly height different from said first fly height; and

performing an additional re-read of data at said first disk location while re-positioning said read head to be off-track by a second off-track amount different from said first off-track amount and at a fly height different from said first normal fly height.

7. A method as claimed in claim 6, further comprising:

positioning said fly height to be different from said first normal fly height only after at least one attempt is made to re-read while said read head is at said first normal fly height.

8. A method as claimed in claim 6, further comprising:

performing the additional re-read of data at said first disk location while positioning said read head so as to be at a fly height different from said second fly height and different from said first normal fly height.