Browse Prior Art Database

Seek Velocity Compensation for Disk File Systems with Variable Tracks Per Meter

IP.com Disclosure Number: IPCOM000115838D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Serrano, J: AUTHOR

Abstract

For disk files with fixed track pitch, the seek velocity profile is a function of tracks to target. A process is disclosed here for extending this method to disk files with a variable track pitch.

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Seek Velocity Compensation for Disk File Systems with Variable Tracks
Per Meter

      For disk files with fixed track pitch, the seek velocity
profile is a function of tracks to target.  A process is disclosed
here for extending this method to disk files with a variable track
pitch.

      Suppose there is a seek velocity profile for a fixed track
pitch version of the disk drive.  This invention uses a quadratic
polynominal of the current and target track to compensate for the
change in track pitch across the disk.

      Suppose that the track pitch at the outer diameter of the disk
(track number 1) is T, and that there is an existing seek velocity
profile based on the track pitch T.  Suppose also that the track
pitch at the  ID (track number N + 1) is (1 + a)T, and that the track
pitch varies linearly with the radius.  If we are currently offset
from track center N1 by a fraction b  of a track, then the
distance-to-go when seeking to track N2 is (in meters)

      Here N0 is the number of tracks of track pitch T that gives
the equivalent distance-to-go.  The desired seek velocity can  now be
determined by using N0 tracks as the distance-to-go in the existing
velocity profile.

      If the track pitch does not vary linearly with radius, then a
series of piecewise linear approximations can be made.