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DUAL WRITE INHIBIT

IP.com Disclosure Number: IPCOM000014119D
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 1 page(s) / 25K

Publishing Venue

IBM

Abstract

Described is a method for improving data reliability using a dual write inhibit technique. One level of write inhibit (the "primary" write inhibit) is exactly like the classic technique: the write operation is stopped if the servo determines the write head is too far off track. The second level (or "secondary" write inhibit) is used to determine when more extensive action is required by the drive.

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DUAL WRITE INHIBIT

   Described is a method for improving data reliability using a dual write
inhibit technique. One level of write inhibit (the "primary" write inhibit) is
exactly like the classic technique: the write operation is stopped if the servo
determines the write head is too far off track. The second level (or "secondary"
write inhibit) is used to determine when more extensive action is required by the
drive.

Writing off-track can cause loss of data in several ways. First, the write
operation may damage data on an adjacent track. Second, the data itself may be
written too far from track center to be read on a subsequent read operation.
Third, the write operation may not overwrite old information on the track, which
a subsequent read operation may then accidentaly read. All three of these errors
result in unrecoverable losses of data. A classic write inhibit technique tries
to prevent data loss by stopping the write before it moves so far from track
center as to cause one of these problems. However, this may not always be
possible. But despite the fact that the servo may not be able to stop the write
in time, it should be able to detect that the off track write did occur. What is
needed then is a way to use this method to prevent any of the hard errors
described above.

The servo system posts write inhibit when it observes that the head is too far
from track center. However, despite this prompt action, the head may still be
so far from track center that there is still an expo...