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Defect Entry with Skew Factor Disclosure Number: IPCOM000127539D
Publication Date: 2005-Aug-31
Document File: 2 page(s) / 7K

Publishing Venue

The Prior Art Database


To realize Spiral Format(No latency sequential access), it is necessary to establish ID table creation concurrently with media access. That is, simple defect entry for ID table creation is required. Defect entry with skew factor can minimize latency of head change of banded format structure on Spiral Format.

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Defect Entry with Skew Factor

The following rule of Spiral Format is true when no head change.

Physial Sector No.0 = Minimum LBA of the track

  Physial Sector MAX = Maximum LBA of the track
And it is no latency completely. Under this condition, current defect entry is referred directly without any handling.

Current defect entry = Pseudo LBA = Defective ABA - Total push count before this ABA

But one revolution latency is required due to head change latency in banded format shown below.

It is impossible to access physical sector 0 of different head from sector MAX of current head without latency.

HD-0 -->--+ -->--+ -->--+

HD-1 +--<-+ +--<-+ +--<-+ V V V
HD-2 +->--+ +->--+ +->--+ V V V
HD-3 ---<-+ ---<-+ ---<-+
It is essential to introduce skew factor to minimize head change latency.

By introducing skew factor, defect entry must be modified according to skew factor to make ID table creation easy on Spiral Format. So "Actual LBA" defect entry is a solution to minimize head change latency.

Actual defect entry = Pseudo LBA with skew factor

"Actual LBA" is calculated from Pseudo LBA by skew factor and PDM (Primary Defect Map) consists of re-ordered "Actual LBA" at manufacturing process.

Disclosed by Hitachi Corporation


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