FFS is one name given to the BSD Fast File System, also known as UFS1 or UFS2 (referring to different versions of the file system). Modern FFS implementations are used in many systems based on 4.2BSD, 4.3BSD and 4.4BSD, including FreeBSD, OpenBSD, and NetBSD. Variants and derivative file systems are also in use on other platforms, including Solaris. Many differences in terms of capabilities and metadata exist between these systems, and compatibility is not guaranteed.
Note: This article refers to the BSD Fast File System. For information on the Amiga Fast File System, please see Ffs (Amiga).