What is fast file system?

Fast File System (FFS) is a file system created by Marshall Kirk McKusick for the BSD Unix operating system family. It was designed to improve the performance of file storage operations by reducing disk drive head movement and improving data locality. FFS is particularly suited for systems that have large volumes of small files, as it uses a hierarchical directory structure that allows for fast directory searches.

One of the key features of FFS is its use of cylinder groups, which divide the disk into contiguous groups of cylinders to reduce head movement. The file system also uses a technique called block mapping, which allows for efficient access to disk blocks and reduces fragmentation.

FFS was first introduced in the 4.2BSD release and has since been used in various versions of Unix and Unix-like operating systems, including FreeBSD, NetBSD, and OpenBSD. It has been widely acclaimed for its reliability, performance, and robustness.