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Protection method for defective servo at read position

IP.com Disclosure Number: IPCOM000016208D
Original Publication Date: 2002-Nov-09
Included in the Prior Art Database: 2003-Jun-21
Document File: 1 page(s) / 59K

Publishing Venue

IBM

Abstract

Disclosed is a method for to avoid defective servo track in read operation. It registers bad servo track for read positioning utilizing detected bad servo track at write positioning in HDD manufacturing test process. It prevents read errors due to defective servo track. IBM HDD has picked up GMR head. The GMR head has a gap what is between write element and read element, it has become separating away. Referring servo track number at read positioning is different from write positioning's one if the gap is over single track width, in this case read positioning still uses defective servo track detected and registered at write positioning. It can be solved that registers both of tracks referred at not only write position, but also read position. The servo track number referred at read position is able to calculate from the write position's one. For the servo related error detectability, write operation is higher than read operation , that is the reason why utilizing defective servo track detected in write operation. Write positioning and read positioning, they referred same track if the read/write gap was less than single track width, however it is wider than single track width now, thus the referred servo track number is different. Refer figure as below

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Protection method for defective servo at read position

Disclosed is a method for to avoid defective servo track in read operation.

It registers bad servo track for read positioning utilizing detected bad servo track at write positioning in HDD manufacturing test process. It prevents read errors due to defective servo track.

IBM HDD has picked up GMR head. The GMR head has a gap what is between write element and read element, it has become separating away. Referring servo track number at read positioning is different from write positioning's one if the gap is over single track width, in this case read positioning still uses defective servo track detected and registered at write positioning. It can be solved that registers both of tracks referred at not only write position, but also read position. The servo track number referred at read position is able to calculate from the write position's one. For the servo related error detectability, write operation is higher than read operation , that is the reason why utilizing defective servo track detected in write operation.

Write positioning and read positioning, they referred same track if the read/write gap was less than single track width, however it is wider than single track width now, thus the referred servo track number is different. ( Refer figure as below )

Head

Track

Fig. Track width vs Read/Write element gap

The read servo track number is calculated by as following formula.

Read servo track = Write servo track...