Browse Prior Art Database

Doubling of Hard Disk Drive Data Capacity in Multimedia Applications

IP.com Disclosure Number: IPCOM000114690D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 101K

Publishing Venue

IBM

Related People

Ottesen, HH: AUTHOR

Abstract

The data characteristics of multimedia (video, audio, image) allow a large capacity increase in the standard hard disk drive using magnetoresistive (MR) heads. By formatting multimedia data in inbound and outbound spirals on alternating disk surfaces, the sector servo tracking capability can be substantially improved due to minimal excitations of mechanical resonances. This allows us to decrease the width of the thin film write head, which was almost twice the MR head width, down to about 1.1 - 1.15 times the MR head width. The reduction in the write width also allows for an increase in the track density by over 70% without sacrificing any MR head signal to noise ratio. Linear density can also be increased for additional gain in areal density and capacity.

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Doubling of Hard Disk Drive Data Capacity in Multimedia Applications

      The data characteristics of multimedia (video, audio, image)
allow a large capacity increase in the standard hard disk drive using
magnetoresistive (MR) heads.  By formatting multimedia data in
inbound and outbound spirals on alternating disk surfaces, the sector
servo tracking capability can be substantially improved due to
minimal excitations of mechanical resonances.  This allows us to
decrease the width of the thin film write head, which was almost
twice the MR head width, down to about 1.1 - 1.15 times the MR head
width.  The reduction in the write width also allows for an increase
in the track density by over 70% without sacrificing any MR head
signal to noise ratio.  Linear density can also be increased for
additional gain in areal density and capacity.

      Traditional Hard Disk Drives (HDD) are designed based on the
typical characteristics of alpha-numeric (ASCII, EBCDIC) data.  Some
of these attributes are: short records, low Soft Error Rates (SER),
frequent short random accesses, short latency times, high data rates,
etc.  In the multimedia (video, audio, image, .... ) environment the
typical characteristics of the data are as follows: very long
records, non-coded compressed data (gray scale or color pixels),
decoded by human eyes and ears, records stored sequentially (could be
spiral), infrequent accesses, long access and latency times are
acceptable, low data rates, etc.  The long compressed data records
allow for spiral tracking operation.  Spiral tracking is conducive to
low excitation of HDD mechanical resonances and this is ideal for
high tracking accuracies.  High tracking accuracies lead to higher
track densities.

      From the above one can see that that the cost of a disk drive
for the "traditional HDD environment" is more expensive than a HDD
for the multimedia environment.  This is due to the requirement of
faster electronics, more power, better tolerances, etc.  It is
therefore a disadvantage to store multimedia information on a
traditional HDD, if other alternatives are available

      This disclosure takes advantage write-wide/read-narrow concepts
used with the MR-heads.  Today's MR-heads have an inductive write
head whose width is approximately twice the width of the MR read
element.  The write element width is roughly 80 - 90% of the width
(pitch) of the data track.  The on-track SER is an exponential
function of the MR stripe width.  The Signal-to-Noise ratio (S/N)
varies proportionally with the MR stripe width.

      When the track density is increased (to a first order
approximation), it is also important not to change to on-track SER.
T...