Hierarchical File System (Apple)

Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs.

It shared a number of design features with MFS that were not available in other file systems of the time (such as DOS's FAT).

However, MFS had been optimized to be used on very small and slow media, namely floppy disks, so HFS was introduced to overcome some of the performance problems that arrived with the introduction of larger media, notably hard drives.

The solution was to replace MFS's directory structure with one more suitable to larger file systems.

[2] HFS also redesigned various structures to be able to hold larger numbers, 16-bit integers being replaced by 32-bit almost universally.

In macOS Sierra (10.12), Apple's release notes state that "The HFS Standard filesystem is no longer supported.

Five structures make up an HFS volume: The Catalog File, which stores all the file and directory records in a single data structure, results in performance problems when the system allows multitasking, as only one program can write to this structure at a time, meaning that many programs may be waiting in queue due to one program "hogging" the system.

Users with many small files, on the other hand, could lose a copious amount of space due to large allocation block size.