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High Performance File System (HPFS)

When Microsoft and Intel created OS/2, they sought to create an operating system that was more capable than the DOS and Windows versions then available. At the time, the only file system widely used on the PC was the FAT file system, which had a number of significant limitations. The FAT file system was restricted in terms of the size of partitions it could support, only allowed 11-character names, and it had none of the organization, security and reliability features that are so important to corporate, business and individual "power" users. To address these concerns, a new file system was created specifically for OS/2: the High Performance File System or HPFS.

HPFS offers many significant improvements over the FAT file system. These include the following:

• Support for long file names (up to 254 characters) and mixed-case file names.
• More efficient use of disk space, since files are stored on a per-sector basis instead of using multiple-sector clusters.
• Better performance due to overall design, including an internal architecture designed to keep related items closer to each other on the disk volume.
• Less fragmentation of data over time, and less need to defragment the file system.

Considering how much more advanced it was than FAT, one might have expected that HPFS would have become quite popular. Unfortunately, HPFS's wagon was hitched to OS/2, and for a number of reasons (many of them related to politics between IBM and Microsoft) OS/2 never really caught on. As interest in OS/2 waned, so did support for HPFS. While early versions of Windows NT (3.51 and earlier) supported HPFS volumes natively, this support was removed in Windows NT 4.0. Support for HPFS volumes can be added to some non-OS/2 operating systems by using third-party support software, but overall this file system seems to be firmly in a "niche status". Many of its features were incorporated into NTFS by Microsoft, one should note--or at least, NTFS has some definite similarities to HPFS.

You can find more information about HPFS by reading this HPFS FAQ, which isn't "official" but seems to be well-written and fairly detailed. This page includes a discussion of the internal architectural characteristics of HPFS volumes. Note that you'll find them easier to understand if you comprehend the internal structures of FAT file systems first. Comprehending NTFS also helps. :^)

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