Browse Prior Art Database

Priming HPFS386 for DASD Limits

IP.com Disclosure Number: IPCOM000113316D
Original Publication Date: 1994-Aug-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 105K

Publishing Venue

IBM

Related People

Yammine, GA: AUTHOR

Abstract

As businesses got involved with computers and software, it became evident that the software, at the time it was developed, did not take into account future operating environments. For example, at the time the FAT file system for the DOS* operating system was developed there were no hard drives in the Gigabyte range. Consequently, the architecture did not take large hard drives into consideration. Similarly, when the HPFS file system for OS/2** was developed, Local Area Networks were not considered. Disk space management within a LAN is essential to its administrator(s). Since the IBM OS/2 LAN Server - Advanced** was an HPFS-based Network Operating System, it was limited by the HPFS architecture and could not therefore natively support directory-based disk space management.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 45% of the total text.

Priming HPFS386 for DASD Limits

      As businesses got involved with computers and software, it
became evident that the software, at the time it was developed, did
not take into account future operating environments.  For example, at
the time the FAT file system for the DOS* operating system was
developed there were no hard drives in the Gigabyte range.
Consequently, the architecture did not take large hard drives into
consideration.  Similarly, when the HPFS file system for OS/2** was
developed, Local Area Networks were not considered.  Disk space
management within a LAN is essential to its administrator(s).  Since
the IBM OS/2 LAN Server - Advanced** was an HPFS-based Network
Operating System, it was limited by the HPFS architecture and could
not therefore natively support directory-based disk space management.
One solution would be to permanently change the HPFS format.  This
could force customers to format their drives in order to use this
feature.  It would also break any backwards compatibility.  A second
solution would be to dynamically initialize the HPFS drive in order
to enable it for disk space management.  This solution enables users
to take advantage of disk space management on HPFS drives without
having to FORMAT their drives - clearly a more appealing approach.

SOLUTION - The nature of disk space management on a per-directory
basis requires  that the file system maintain the current size of
each directory at all times.  This information is not part of the
HPFS format.  Consequently, it has to be generated before the
function itself can be used.  The mechanism that initializes an HPFS
volume, or drive, for disk space management Limits is called priming.

The priming mechanism is as follows:

1.  The administrator issues a command to enable disk space
    management on a particular HPFS drive.

2.  The file system receives the request and places the drive in
    INSTALL mode.  This mode indicates that the function is being
    enabled on the volume but is not yet complete.  Disk space
    management on the drive remains inactive until the installation
    process is complete.

3.  As part of the installation process, the file system receives a
    request to re-mount the particular drive.  At this stage, the
    file system checks the mode.  If the drive is in INSTALL mode
    then the file system primes the volume for disk space management.
    If the priming process is successful, then the file system places
    the volume in RUNNING mode.  This means that disk space
    management is now fully operational on the volume.

      To prime an HPFS volume for disk space management, the file
system has to calculate the size of each directory and write the
value to disk.  To accomplish this, it traverses the entire directory
tree in a non-recursive algorithm so that it does not exceed its
allocated stack segment.  The algorithm below describes how the file
system traverses...