Browse Prior Art Database

Programmable Softfile Interleave

IP.com Disclosure Number: IPCOM000114625D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 99K

Publishing Venue

IBM

Related People

Kandefer, FK: AUTHOR

Abstract

A method for doing a programmable interleave to enhance disk access time is disclosed. The software is programmed to match the characteristics of the disks operating environment, without changing any of the hardware characteristics of the disks. This software algorithm allows optimum disk performance, while using existing hardware technologies.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Programmable Softfile Interleave

      A method for doing a programmable interleave to enhance disk
access time is disclosed.  The software is programmed to match the
characteristics of the disks operating environment, without changing
any of the hardware characteristics of the disks.  This software
algorithm allows optimum disk performance, while using existing
hardware technologies.

      Many existing floppy disk technologies do not meet the
performance needs of todays software programs.  By observing the
hardware characteristics of most floppy disks, an algorithm that
allows software to increase the performance of the disk operations
was determined.  This increase in performance comes without requiring
changes in hardware or sacrificing media interchange (format
changes).

      In observing the hardware characteristics of the floppy disk,
the majority of the time is lost because of the time it takes to spin
the disk to get to the next sector of data.  This can be as much as
one full revolution of the disk, since sectors are normally accessed
in sequential order.  To reduce the time lost waiting, an interleave
algorithm was invented.

      The basic idea is to access the sectors in non-sequential order
(interleaved order).  This allows the software to access the next
available sector, instead of waiting for the next sequential sector.
The software needs to inimize the wait time for the next available
sector, without missing the sector.  Missing the sector means another
lost revolution of the disk.

      Today, some software programs may attempt to account for this
function, however the interleave value is usually fixed and can not
be modified to fit the environment.  Many things affect the execution
time of the software and the time it takes the hardware to move to
the next sector.  However, a simple programming algorithm allows the
software handling the interleave function to be adjusted to the
environment.  The following describes his method.

      An interleave variable can be passed or setup via an End User
Interface.  This is the interleave (skip) variable that the software
uses to adjust to the environment it lives in.  For example, if the
variable is set to 2 then ever other sector is accessed.  In this
example, the software must process the first sector in the time it
takes the hardware to revolve past the next sector.  If the software
completes before the third sector is under the disk head, then the
interleave value is good.  If the processing time takes longer then
the time it takes for the hardware to move past the following sector,
then the interleave variable needs to be adjusted.  Of course, the
larger the interleave variable the more revolutions of the disk it
takes to access all requested sectors.  For example, an interleave of
two requires two revolution to assess a...