Amiga Fast File System

Amiga Fast File System

The Amiga Fast File System (FFS; not to be confused with the identically named Berkeley Unix FFS) is a file system used on the Amiga personal computer. The Amiga Old File System (OFS) was too slow to keep up with hard drives. FFS differs mainly in the removal of redundant information. Data blocks contain nothing but data, allowing the filesystem to manage the transfer of large chunks of data directly from the host adapter to the final destination.

History

FFS was introduced with version 1.3 of AmigaOS [ [http://www.gregdonner.org/workbench/wb_13.html Workbench Nostalgia; history of the AmigaOS GUI: Release 1.3 ] ] in 1988 [ 1.3 release confirmed on September 16, 1988 by Carolyn Scheppner of CATS in amiga.dev in BIX. [http://groups.google.co.uk/group/comp.sys.amiga/msg/f8a849922796bc93 Copy of BIX announcement from USENET] ] .

AmigaOS 3.0, designed for the Amiga 4000, introduced two new FFS modes:
* International mode allows FFS to handle filenames with international characters.
* Directory Cache mode allows the filesystem to access hard disks more rapidly by creating a cache of directory contents.As any other directory caching based systems it used a certain amount of disk space to store the data.

More recently, MorphOS and AmigaOS 4 have introduced support for a slightly updated Fast File System 2, or FFS2.

Like the normal (or "ancient") FastFileSystem, FFS2 is outdated compared to more modern file systems. It lacks the reliability and advanced features of more modern offerings. All FFS versions store a "map" of the filesystem in a bitmap which is prone to deletion or corruption if the OS is reset or crashes during a write, resulting in data loss or invalidation of the filesystem.

FFS2 is a minor update of FastFileSystem for AmigaOS 4 and MorphOS. It implements long filename support while maintaining backward compatibility with the older FastFileSystem and OldFileSystem. However its only major addition is the capability of handling longer filenames, and still suffers from the negative points of FFS. It is still supported only for legacy purposes.

Characteristics

The Amiga Old File System article, in the section "Characteristics", presents the basic information regarding Amiga filesystems specifications.

As with OFS, FFS suffers from one major drawback. Because they write to a disk bitmap, if the OS crashes during this write, the filesystem can become invalidated. While AmigaOS features a built in disk validator (it was external prior to AmigaOS 2), validating volumes can take a very long time, especially if they contain a lot of files. It is also possible to lose data. While the disk is being validated, other disk access is very slow, and the volume is write protected. The disk validation process is normally successful, but in rare cases it will fail and require the use of tool such as DiskSalv to repair the damage and validate the volume. Disk validation is still necessary in FFS2.

References

ee also

*OFS
*Professional File System
*Smart File System
*List of file systems

External links

* [http://lclevy.free.fr/adflib/index.html The ADFlib Page] and precisely [http://lclevy.free.fr/adflib/adf_info.html ADF File specs]
* [ftp://it.aminet.net/pub/aminet/disk/misc/ADFlib.lha The ADF specs] , in LHA format from Aminet


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