HPFS
The High-Performance File System (HPFS) was developed by Microsoft and IBM for OS/2, a joint operating system released in the late 1980s. HPFS was designed to address the limitations of the File Allocation Table (FAT) system by improving performance, supporting larger file sizes, and offering enhanced file management features.
While it has since been largely replaced by more modern file systems like NTFS and exFAT, HPFS played a crucial role in the evolution of file storage. In this article, we will look deeply into how HPFS revolutionized file storage patterns, its architecture, advantages, and limitations. It is important to learn about Windows file systems to be able to understand how they work, and why you may want to pick a particular file system to format your storage disks.
Introduction to the HPFS File System
Introduced in 1988, HPFS launched as part of OS/2 1.2. The High-Performance File System is a pivotal file system format and a precursor to the New Time File System (NTFS); it really set the pace for NTFS to run.
In the late 1980s, Microsoft and IBM partnered to create a new windowing system called the OS/2 to override the limitations of FAT and allow for more extensive support; this birthed the HPFS format, which stands for High Performance Filesystem. So, the HPFS supports long filenames and small cluster sizes, as well as removing fragmentation. Basically, the HPFS is everything NTFS is, excluding the embedded security features on NTFS.
The HPFS stores data in sorted B-Tree’s, thus speeding up file searches. However, HPFS retained the directory organization of FAT with the addition of an automatic sorting algorithm for directories based on filenames; with HPFS, filenames can reach 254 double-byte characters. It also bands descriptor files and directory tables at regular intervals throughout a disk and in the middle of the disk, following the theory that heads only have to move half as much in any direction.
Key Features of HPFS
- Longer Filenames: Unlike FAT, which had an 8.3 filename limitation (eight-character name with a three-character extension), HPFS allowed filenames up to 255 characters.
- Efficient Disk Utilization: HPFS minimized file fragmentation and used a more efficient method for allocating disk space, contributing to improved performance.
- B-tree Directory Structure: The file system employs a B-tree directory structure, allowing faster searching and retrieval of files compared to the linear search method used in FAT.
- Improved File Allocation: HPFS stored file data in contiguous blocks whenever possible, reducing fragmentation and enhancing read/write speeds.
- Metadata Storage in Extended Attributes: Unlike FAT, HPFS supported extended attributes, allowing additional file metadata to be stored alongside standard file information.
- Improved Reliability: HPFS implemented features like a superblock (containing critical file system information) and a spare sector to improve data reliability and reduce file corruption risks.
- Support for Large Volume Sizes: HPFS was capable of supporting volume sizes up to 2 TB, which was a significant improvement over FAT-based file systems of its time.
Hotfixing for Better Fault Tolerance: HPFS incorporated a hotfixing mechanism with the spare blocks feature, which allowed the file system to detect and work around bad sectors dynamically—moving files from a bad sector to a good (spare) one.
Structural Highlights of HPFS
HPFS’s architecture is different from FAT and more advanced for its time. The main components were:
- Super Block: Located at sector 16 of the disk, the superblock stores essential information about the file system, including volume size, allocation structure, and metadata. This spare block helps for hotfixing on HPFS drives.
- Directory Structures: Instead of linked lists, HPFS uses a B-tree structure for directories.
- Allocation and Clustering: HPFS uses 512-byte sectors rather than clusters.
- Spare Sectors: Spare sectors are reserved in case of bad sectors, to help improve data reliability.
5. Extended Attributes (EAs): HPFS supports EAs that allow applications to store additional metadata about files, such as security permissions and document descriptions. HPFS can keep 64 KB of extended attributes per file.
HPFS vs. Other File Systems
HPFS is just like every other file system but has its own unique features that make it stand out. Here’s a comparison with other Windows native file systems.
1. HPFS vs. FAT16
FAT is Windows’ first file system; it’s far too old and has many limitations. Although still used up to this day, FAT is no match for newer file systems. In comparison with HPFS, FAT is slower and less capable. HPFS is significantly faster, thanks to its B-tree structure, and it also supports larger file sizes than FAT. HPFS is equally more reliable due to the extended attributes and spare block features.
2. HPFS vs. NTFS
NTFS is a real challenger for HPFS, and being a newer file system, you will expect it to be better. Well, NTFS is actually better than HPFS and supports more modern features. Moreover, NTFS is a journaling file system, which gives it an edge in guaranteeing higher file protection against data corruption. In terms of file security, NTFS supports ACLs and encryption, while HPFS doesn’t. While HPFS can hold up against NTFS, the latter is much better and more reliable.
3. HPFS vs. exFAT
Seeing that FAT is well limited, Microsoft went on to launch extended FAT, commonly called exFAT. This newer edition of FAT is more widely compatible across modern operating systems, including Linux and macOS. However, exFAT is mainly meant for external drives; it acts as a bridge between FAT32 and NTFS.
Comparing HPFS with exFAT, while the former supports up to 2 GB files and partitions, the latter supports files and partitions up to 16 EB (exabytes) and can be used for flash-based storage like USB devices, SD cards, and others. exFAT is still widely used today, while HPFS is obsolete.
Compatibility and Usage of HPFS Today
With the release of Windows NT and NTFS, HPFS gradually became obsolete. Microsoft discontinued HPFS support in Windows NT, favoring NTFS due to its superior security, journaling, and performance capabilities. OS/2 remained its primary user, but as OS/2 lost popularity, so did HPFS.
Today, HPFS is mostly of historical interest, though some niche applications still use it for legacy systems and data backup/recovery purposes. But it is generally no longer in use, as no modern system is compatible with the file system, except older OS/2 systems.
How to Access HPFS Volumes on Modern Systems
It’s rare to find anyone keeping drives formatted in HPFS these days, but just in case you bump into some. The only way to open the disk or partition is by using specialized software tools designed to emulate older Windows OS versions and access older file systems. Modern systems and OSes cannot read an HPFS partition or disk, sadly. You can run the obsolete OS/2 on a virtual machine and then access the HPFS disks from there.
Well, some data recovery software programs support the HPFS file system, which means you can use such programs to recover your files from the HPFS volume and save them elsewhere. DiskInternals Partition Recovery is one of those programs to try out for this purpose.
Common Issues with HPFS and Troubleshooting Tips
Although HPFS (High-Performance File System) was a major improvement over FAT when it was introduced in the OS/2 operating system, it has since become outdated. If you're still using HPFS, you may run into several issues related to compatibility, corruption, and performance. Below are some of the most common HPFS problems and how to troubleshoot them.
HPFS Volume Not Recognized
HPFS is primarily supported by OS/2 and early versions of Windows NT (3.1, 3.5, 3.51, and 4.0). You have to run these old OS versions to access the HPFS volume, or try installing third-party HPFS drivers for Linux and see if the system will read the volume. Another option is to reformat the volume to NTFS, but you will lose everything saved in it if you format it.
Sluggish Performance on Large Drives
HPFS was optimized for hard drives not bigger than 2 GB in capacity. The B+ tree structure used for file management slows down when dealing with large amounts of data. So, try to defragment the HPFS drive or keep the partitions under 2 GB each.
Disk Read/Write Errors
Since the HPFS file system is no longer supported by modern hardware, even if your VM or system reads the volume, you may constantly get read/write error notifications. The best solution here would be to copy your files to another storage medium before the issue worsens.
Conclusion
The HPFS file system was a significant step forward in file system technology when it launched, but today, it’s obsolete. Its replacement, NTFS, and other modern file systems are far better in all aspects and feature support. It is not advisable to use HPFS in this current time and age.