Browse Prior Art Database

Attaching Drives to Computer Systems

IP.com Disclosure Number: IPCOM000116216D
Original Publication Date: 1995-Aug-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 85K

Publishing Venue

IBM

Related People

Fleney, JM: AUTHOR [+2]

Abstract

Normally, operating systems such as DOS or OS/2* assign logical drive letters to physical drives depending on the number of physical drives attached to the host computer and the number of logical partitions that each physical drive contains. Thus, moving a drive from one machine to another usually means that unless the second machine is exactly the same configuration as the first, then the logical drive identifiers assigned to the disk will be different.

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

Attaching Drives to Computer Systems

      Normally, operating systems such as DOS or OS/2* assign logical
drive letters to physical drives depending on the number of physical
drives attached to the host computer and the number of logical
partitions that each physical drive contains.  Thus, moving a drive
from one machine to another usually means that unless the second
machine is exactly the same configuration as the first, then the
logical drive identifiers assigned to the disk will be different.

      In a number of situations it is desirable to allow a physical
drive to maintain the logical drive letters assigned to it regardless
of which machine it is installed in.  Drives can then be added to a
machine without the need for a reboot of the system.  This allows
data or application environments to be ported from machine to machine
without altering the environment of the recipient machine in any way.

      The arrangement disclosed here uses two discrete pieces of
software, a device driver which runs when the operating system is
processing the user's CONFIG.SYS file, and an executable file which
runs during the processing of AUTOEXEC.BAT, to provide such an
enhanced
facility.

      The device driver has the responsibility for controlling all
accesses to and from the drives under its control.  During its
initialization routine, the driver reads the partition tables of all
physical drives attached to the machine and takes control of all
partitions that are marked as being part of a drive for which the
enhanced facility is required.  It creates BIOS PARAMETER BLOCKS for
each drive and returns status to the operating system kernel,
detailing how many drive letters it has used.  The operating system
kernel builds the required internal control blocks for each drive
letter.  The device driver also sets up a user timer_tick routine,
which is given control every 55 milliseconds by the kernel.  This
routine monitors when the processing of CONFIG.SYS is completed.
When true, the LOGICAL DRIVE TABLES (LDT) set up by the operating
system are moved from the OS segment to storage controlled by the
device driver and the OS internal pointers to those tables...