The Smart File System (SFS) is a

journaling filesystem A journaling file system is a file system that keeps track of changes not yet committed to the file system's main part by recording the goal of such changes in a data structure known as a "journal", which is usually a circular log. In the even ...

used on

Amiga Amiga is a family of personal computers introduced by Commodore International, Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and sign ...

computers and

AmigaOS AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early versions ...

-derived

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

s (though some support also exists for

IBM PC compatible IBM PC compatible computers are similar to the original IBM PC, XT, and AT, all from computer giant IBM, that are able to use the same software and expansion cards. Such computers were referred to as PC clones, IBM clones or IBM PC clones ...

s). It is designed for performance,

scalability Scalability is the property of a system to handle a growing amount of work by adding resources to the system. In an economic context, a scalable business model implies that a company can increase sales given increased resources. For example, a ...

and integrity, offering improvements over standard Amiga filesystems as well as some special or unique features.

Features

SFS uses block sizes ranging from 512 (2⁹) to 32768 (2¹⁵)

byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...

s 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 In computing, a bitmap is a mapping from some domain (for example, a range of integers) to bits. It is also called a bit array or bitmap index. As a noun, the term "bitmap" is very often used to refer to a particular bitmapping application: t ...

is used to keep track of free space, and file data is kept track of using extents arranged into a

B+ tree A B+ tree is an m-ary tree with a variable but often large number of children per node. A B+ tree consists of a root, internal nodes and leaves. The root may be either a leaf or a node with two or more children. A B+ tree can be viewed as a ...

structure. Integrity is maintained by keeping a

transaction log In the field of databases in computer science, a transaction log (also transaction journal, database log, binary log or audit trail) is a history of actions executed by a database management system used to guarantee ACID properties over crashes ...

of all changes made to metadata over a certain period of time. The log is written to disk first into free space and then meta data blocks are overwritten directly. Should the system crash, the next time the filesystem is mounted it will notice the uncompleted operation and roll it back to the last known consistent state. For performance reasons, only metadata integrity is ensured. Actual data in files can still be corrupted if a write operation is terminated halfway through. Unlike the original Amiga filesystems, FFS and OFS, filesystem integrity is very rarely compromised by this. One feature of SFS that is almost unique among Amiga filesystems is its ability to defragment itself while the filesystem is in use, even for locked files. The defragmentation process is almost completely stateless (apart from the location it is working on), which means it can be stopped and started instantly. During defragmentation data integrity is ensured of both meta data and normal data. The filesystem may attempt to move a whole file to a different location when fragmentation is going to occur otherwise. The filesystem offers a directory containing deleted files for recovery.

History

SFS is written in C and was originally created and released as

freeware Freeware is software, most often proprietary, that is distributed at no monetary cost to the end user. There is no agreed-upon set of rights, license, or EULA that defines ''freeware'' unambiguously; every publisher defines its own rules for the ...

in 1998 by John Hendrikx. After the original author left the Amiga scene in 2000, the source code to SFS was released and its development continued by Ralph Schmidt in

MorphOS MorphOS is an AmigaOS-like computer operating system (OS). It is a mixed proprietary and open source OS produced for the Pegasos PowerPC (PPC) processor based computer, PowerUP accelerator equipped Amiga computers, and a series of Freescale dev ...

. Since May 2005 SFSobjec and SFSconfig are available under the GPL license. SFS development has now forked; as well as the original Amiga version, there are now versions for

AROS Aros may refer to: *Aros (Middle-earth), a river in J. R. R. Tolkien's Middle-earth legendarium * Aros, Mull, the location of Aros Castle, a ruined 13th-century castle on the Isle of Mull, Scotland *AROS Research Operating System, a free software i ...

, AmigaOS 3, and a version for

AmigaOS 4 AmigaOS 4 (abbreviated as OS4 or AOS4) is a line of Amiga operating systems which runs on PowerPC microprocessors. It is mainly based on AmigaOS 3.1 source code developed by Commodore, and partially on version 3.9 developed by Haage & Partne ...

, which have different feature sets but remain compatible to each other. In addition, there is a driver for

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...

to read (experimental to write) Amiga SFS volumes, GRUB natively supports it, and there are free drivers to use it from

UEFI UEFI (Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. Examples ...

. , SFS was one of the independent filesystems still being used on Amiga computers. Versions for

and

are based on different branches. The Linux version is independent code.

References

External links

Original SFS site
includin

*
OS4 SFS site
* {{File systems Disk file systems Amiga software AmigaOS 4 software AROS software MorphOS

Features

History

See also

References

External links