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Browse Prior Art Database

Optimization of Look-Ahead Abort Timing

IP.com Disclosure Number: IPCOM000111505D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Tasaki, M: AUTHOR

Abstract

This article describes a micro code program of hard disk drives which maximizes buffer usage. This program determines the optimum time to abort the previous look-ahead operation when the incoming read command does not hit the buffer.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 78% of the total text.

Optimization of Look-Ahead Abort Timing

      This article describes a micro code program of hard disk drives
which maximizes buffer usage.  This program determines the optimum
time to abort the previous look-ahead operation when the incoming
read command does not hit the buffer.

      Hard disk drives have buffers to efficiently communicate with
the host.  They maintain the read data in the buffer and sometimes
read the consecutive sectors after they return data for a read
command.  Presuming that the buffer is divided into plural small
buffers and they are used as individual buffers, it is effective to
maintain plural individual data.

      When the host sends sequential read commands with some random
read commands, all read commands will not hit the prefetched data.
So, the drive sometimes aborts the look-ahead operation to access the
media for the incoming read command.  Then, it seeks the requested
cylinder to wait for the requested sector on the cylinder.  The seek
time and the latency are inevitable.

      In this case, the drive aborts the previous look-ahead
operation before the buffer becomes full.  This abort operation
reduces the chance for the next command to hit the buffer.

      With this program, the drive will not abort the look-ahead
operation when it receives a read command that does not hit any of
the buffers.  This program calculates the seek time and the latency
from the current reading position (cylinder, head and sector...