The HPFS FAQ

License: Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Introduction

Since I can't resist answering questions about HPFS in various news groups, I've finally taken the time to collate some of the most commonly-asked questions and answers. Further questions (and even answers) are welcome by email to lesbell@lesbell.com.au. All contributions will be credited.

What Is the High Performance File System?

HPFS is OS/2's preferred, native file system or disk format.

When OS/2 1.0 first shipped, in the rush to get it out the door, Microsoft took developers off one part of the operating system and put them to work on other components. The part that took the schedule hit was HPFS, and so OS/2 1.0 shipped with the same disk format and file system code as DOS - the FAT (File Allocation Table) File System. Performance was less than impressive, and did not help OS/2 win customers over DOS.

In OS/2 1.2, however, Microsoft and IBM finally caught up and introduced support for Installable File Systems. An IFS is a special kind of dynamic link library which provides support for a disk format and hooks into the kernel's file system router, throught the IFS= statement in CONFIG.SYS.

Several installable file systems are available for OS/2:

HPFS - the High Performance File System
CDFS - the CD-ROM File System
NETWKSTA - the LAN Server remote file system
HPFS386 - the LAN Server Advanced network version of HPFS
HPOFS - the High Performance Optical File System
SRVIFS - The CID remote installation thin file system

HPFS provides a variety of advantages over the FAT file system.

What are the Benefits of HPFS over FAT?

Support for long file names - up to 254 characters in length
upper and lower case - HPFS preserves case, but is not case sensitive
extended character sets
Native (non-fragile) support for EA's: FAT is just _too_ fragile to support this, and the workplace shell depends on it heavily.
Higher performance. FAT degrades rapidly as drive size goes up. HPFS degrades a lot less. FAT degrades rapidly with lots of files in directories, HPFS degrades a lot less. Try unzipping an i