Browse Prior Art Database

OS/2* Raw File System

IP.com Disclosure Number: IPCOM000118714D
Original Publication Date: 1997-May-01
Included in the Prior Art Database: 2005-Apr-01

Publishing Venue

IBM

Related People

Kreulen, JT: AUTHOR

Abstract

Operating Systems used under heavy workloads, such as on-line transaction processing, can become CPU and I/O bound. Under these circumstances, the file system becomes critical to maximizing the performance. Disclosed is an invention which alleviates the CPU instruction pathlength problem by providing raw access to physical and logical disk drives. Additional improvements were also achieved by adding the capability to submit multiple requests in one operation system call.

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OS/2* Raw File System

      Operating Systems used under heavy workloads, such as on-line
transaction processing, can become CPU and I/O bound.  Under these
circumstances, the file system becomes critical to maximizing the
performance.  Disclosed is an invention which alleviates the CPU
instruction pathlength problem by providing raw access to physical
and logical disk drives.  Additional improvements were also achieved
by adding the capability to submit multiple requests in one operation
system call.

INTRODUCTION

      The OS/2* raw file system provides an interface for
applications to efficiently manage data on the logical partitions or
physical hard drives installed in a system.  Some of the raw file
system function is available by using a combination of the
DosPhysicalDisk and  DosDevIoctl application programming interfaces.
However, the current raw file system provides a significant step
forward in usability and performance.

      The OS/2* raw file system provides a programming abstraction
that treats each logical partition or physical disk as one large file
that can be opened, locked, seeked, read from, written to, and
closed.  Logical partitions are identified using the Universal Naming
Convention (UNC) in the form of '\\.\X:', where 'X' can be
substituted with the letter corresponding the logical partition
desired on any hard  drive, floppy disk, or CD-ROM drive.  Physical
disks are identified using UNC naming in the form of
'\\.\Physical_Disk ', where ' ' is replaced with the physical disk
number corresponding to the number found  in the FDISK utility.  The
combination of the naming convention and use  of the common file
system Application Programming Interfaces (APIs) provides a greatly
simplified migration path for applications.

      Traditionally, raw file systems have been utilized by
applications that manage large amounts of data under heavy
workloads.  Typically, this has been commercial database servers
performing on-line transaction processing.  Disk I/O can become a
bottleneck under these conditions and the use of an efficient raw
file system can be very useful in improving system performance,
through reduced path length and serialization.  The purpose of this
disclosure is to describe in detail the used by the OS/2 raw file
system and how to  use them.

      Programming Recommendations

      As an aid to those who wish to develop using the OS/2 raw
file system, the following are a few recommendations based on the
implementation that will help make the most of your efforts:
  o  Caution!  Please be careful when using the raw file system.
      While it can be very useful and powerful, it will not stop
      you from destroying the data on your disks if you are not
      careful.
  o  Physical Disk Numbering - Physical disk numbers correspond
      directly with the number assigned using the FDISK utility
      program.
  o  Physical Disk Formattin...