The Smart File System (SFS) is a journaling filesystem used on Amiga computers and AmigaOS-derived operating systems (though some support also exists for IBM PC compatibles). It is designed for performance, scalability and integrity, offering improvements over standard Amiga filesystems as well as some special or unique features.
SFS uses block sizes ranging from 512 (29) to 32768 (215) bytes with a maximum partition size of 128 GB. Its good performance, better than FFS, and lack of need for long "validation" in case of an error, is achieved by grouping multiple directory entries into a single block and by grouping meta data blocks together into clusters. A bitmap is used to keep track of free space, and file data is kept track of using extents arranged into a B+ tree structure. (Full article...)