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Fast Write Disk Drive Architecture with Position Error Signal Table

IP.com Disclosure Number: IPCOM000119186D
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 108K

Publishing Venue

IBM

Related People

Dang, HP: AUTHOR [+5]

Abstract

Disclosed is a device that reduces the write access times in hard disk drives by permitting the write process during the settle out process of the head. A "PES Table" consisting of the Position Error Signal (PES) information of the latest write access profile is stored in the disk and is used during the read process to follow the write profile instead of the track center. This permits the head to follow the written bits precisely and to recover data reliably. The width of the guard band between adjacent tracks can be increased to further relax write times, thereby providing a compromise between performance and capacity.

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Fast Write Disk Drive Architecture with Position Error Signal Table

      Disclosed is a device that reduces the write access times in
hard disk drives by permitting the write process during the settle
out process of the head.  A "PES Table" consisting of the Position
Error Signal (PES) information of the latest write access profile is
stored in the disk and is used during the read process to follow the
write profile instead of the track center.  This permits the head to
follow the written bits precisely and to recover data reliably.  The
width of the guard band between adjacent tracks can be increased to
further relax write times, thereby providing a compromise between
performance and capacity.

      Write access times for disk drives are generally significantly
longer than corresponding read access times to ensure reliable
storage and retrieval of data.  Most of the write access time is
spent in waiting  for the head to settle inside a small zone around
the track center as shown in Fig. 1-a.  This ensures that the data
written on the track will  not be offset from the track center by
more than the allowable zone width.  Thus, while reading the data,
the head is set to follow the center of the track, as shown in Fig.
1-b.

      At present, there is no mechanism to improve the write access
time, other than improvement in the overall servo mechanics.  By
simply starting the write process early, user information will be
offset from  the center of the track.  At best this makes the
retrieval of data during  the read process difficult, since signal
levels from the offset data will  be smaller.  In the worst case,
data can be written when the head is significantly offset from the
center of track, wherein the data can spill  over the guard band and
overwrite data on the neighboring tracks.

      This architecture permits a Fast Write process by relaxing the
width of the allowable settl...