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Idle Algorithm Optimized for Seek Compliance

IP.com Disclosure Number: IPCOM000115928D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 68K

Publishing Venue

IBM

Related People

Gopalakrishna, S: AUTHOR [+2]

Abstract

Idle algorithms are usually optimized to have the heads flying at the maximum Fly Height Tolerance (FHT) for the cylinders upon which the file track follows. It is proposed that the cylinders be selected such that when the customer seeks to get data after idle, the FHT modulation is optimized.

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Idle Algorithm Optimized for Seek Compliance

      Idle algorithms are usually optimized to have the heads flying
at the maximum Fly Height Tolerance (FHT) for the cylinders upon
which the file track follows.  It is proposed that the cylinders be
selected such that when the customer seeks to get data after idle,
the FHT modulation is optimized.

      Idle algorithms are built into many DASD products.  Safe III is
an example in 3390.  Latch products also have programmed motion
during inactive periods.  Usually they involve moving the heads
across the entire disk on a regular basis.  Often they limit having
extended track following by parking in randomly selected cylinders
(Target Cylinders).

      However, by targeting a specific range of cylinders either at
the Inner Diameter (ID) or Outer Diameter (OD) (depending upon the
air bearing design) for track following after the sweep, the stress
on the head-disk interface can be minimized.  For example, it is
well-known that most air bearings behave asymmetrically during seeks.

      Fig. 1 shows a fly height profile  for a first slider design.
The head-to-disk spacing is shown in Fig. 2.  Clearly the ID-to-OD
seek in this instance is less stressful than the OD-to-ID seek.  For
this ABD design, the target track where the actuator waits for the
seek command is selected to be in the ID region.  This design has a
reasonably flat FHT profile so there is little risk of flying at too
low an FHT.

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