Editing Amiga Fast File System (section)

==FFS Modes==
FFS operated in several modes, defined as and by "DOS types". AmigaOS filesystems are identified by a four letter-descriptor which is specified either in the RDB or a so-called ''mountlist'' or ''dosdriver''; alternatively (as was the case in ''trackdisk''-like devices like floppy disks), the disk itself could be formatted in any DOStype specified.

The FFS-DOStypes introduced with AmigaOS v1.3 (v34) were as follows:<ref>AmigaOS user manual 3.1</ref>
{| class="wikitable"
|-
! style="width: 5%"| DOSType
! Type
! style="width: 15%"| AmigaDOS
|-
| <code>DOS\'''0'''</code>
| The former filesystem, ''Original File System'' (OFS).
The filesystem the Amiga used until then – Then consequently referred to as ''Original File System'', short OFS.
| {{nowrap|AmigaOS v1.0–v1.2}}
|-
| <code>DOS\'''1'''</code>
| The new filesystem, ''FastFileSystem'' (FFS).
The first, disk-based release of FFS – The original FastFileSystem did not offer any additional modes.
| {{nowrap|AmigaOS v1.3–v2.0}}
|-
| colspan="3" | The former primary Amiga filesystem, now called OFS, was taken over and integrated into FFS using the first DOS Type DOS\0 for purposes of backward-compatibility.
As the majority floppy-disks shipped by software-companies or as magazine-coverdisks still used this DOS type (which would boot on pre-2.x machines like the Amiga 500), this enabled users with existing OFS-formatted drives, that all older OFS-based disks could still be read afterwards, once they had installed FFS to the RDB of their start-disk.
|-
| colspan="3" style="background-color:#d7dfe4" | '''Note:''' Although DOSType <code>DOS\0</code> is based on the former OFS, this FFS-mode is still <u>not</u> backward-compatible with ''Workbench'' below 2.0.<ref name="Amiga_OS_3.1_Workbench_FFS-reference0">{{cite book |author=AMIGA Technologies GmbH |date=1995 |title=AMIGA OS 3.1 Workbench |publisher=Escom AG |quote=Fast File System disks are incompatible with Workbench software releases prior to 2.0 and should not be selected for disks that are also used on pre-Release 2 Amigas. |page=84 |url=https://archive.org/details/EscomAmigaOS3.1Workbench/page/n83/}}</ref>
|}

AmigaOS 2.04 made FFS (now v37) part of the Kickstart ROM and introduced new modes for handling international characters in filenames,<ref>All Amiga file systems can handle international characters but prior to the International versions they treated upper and lower cased letters as completely distinct characters.</ref> and for an on-disk directory [[Cache (computing)|cache]]. Each new mode was available with both OFS- and FFS-DOSTypes. This odd system was for reasons of parity: OFS-modes apart from <code>DOS\0</code> were almost never used but were available nonetheless.

The new FFS-DOStypes introduced with AmigaOS v2.04 (v37):
{| class="wikitable"
|-
! style="width: 5%"| DOSType
! Type
! style="width: 15%"| AmigaDOS
|-
| <code>DOS\'''2'''</code>
| Mode ''International'' (OFS-INTL) for the former OFS.
Allows OFS the use of international characters.
| {{nowrap|AmigaOS v2.04–v3.0}}
|-
| <code>DOS\'''3'''</code>
| Mode ''International'' (FFS-INTL) for the new FFS.
Allows FFS the use of international characters – This was the most commonly used FFS-mode overall.
| {{nowrap|AmigaOS v2.04–v3.0}}
|-
| colspan="3" | The "International"-mode of the respective DOS-Types enabled both file-systems the use of international characters and thus the handling of file- and folder-names with characters, which are <u>not</u> found in English Latin character-set ([[ISO/IEC 8859-1]]), such as ä, ê, î, ö and ü.
→ All higher DOS-Types have International-mode integrated by default
|-
| colspan="3" style="background-color:#d7dfe4" | '''Note:''' Although DOSType <code>DOS\2</code> is based on the OFS, that Int'l mode-extension is still <u>not</u> backward-compatible with purely OFS-based Amiga-systems without FFS.<ref name="Amiga_OS_3.1_Workbench_FFS-reference_Intl">{{cite book |author=AMIGA Technologies GmbH |date=1995 |title=AMIGA OS 3.1 Workbench |publisher=Escom AG |quote=International Mode is incompatible with Workbench software releases prior to 2.0 and should not be selected for disks that are also used on pre-Release 2 Amigas. |page=84 |url=https://archive.org/details/EscomAmigaOS3.1Workbench/page/n83/}}</ref>
|}
|}

The last published major version of FFS by Commodore (v39), saw the following FFS-DOSTypes being introduced with AmigaOS v3.0:
{| class="wikitable"
|-
! style="width: 5%"| DOSType
! Type
! style="width: 15%"| AmigaDOS
|-
| <code>DOS\'''4'''</code>
| Mode ''Directory Cache'' (OFS-DC) for the former OFS.
Allows OFS the use of primitive directory-caching.
| {{nowrap|AmigaOS v3.0–v3.1}}
|-
| <code>DOS\'''5'''</code>
| Mode ''Directory Cache'' (FFS-DC) for the new FFS.
Allows FFS the use of primitive directory-caching.
| {{nowrap|AmigaOS v3.0–v3.1}}
|-
| colspan="3" | This mode enables primitive directory-caching, by creating dedicated directory-lists instead of having to pick up the linked directory/file entries that lie scattered over the disk. A certain (small) amount of disk space to store the directory data is allocated.<ref>{{cite web|url=http://www.amigahistory.co.uk/adfaq.html#p47|title=Amiga History Guide|website=www.AmigaHistory.co.uk|access-date=May 1, 2017}}</ref>

The ''DirCache''-option improved directory reading-in speed drastically but creating, deleting and renaming files became slower.<br />
It did <u>not</u> increase the speed of reading individual files.

It became a popular choice on Amiga hard drives, but according to Olaf Barthel, author of FFS2, the use of ''DirCache'' modes was probably better suited for floppy disks than it was for hard drives, where it would cause an overall degradation in performance compared to lack of dircache.<ref>{{Cite web | url=http://wiki.amigaos.net/wiki/DCFS_and_LNFS_Low_Level_Data_Structures#Limitations_and_drawbacks | title=Limitations and Drawbacks in DCFS modes - AmigaOS Documentation Wiki | website=wiki.amigaos.net | language=en | access-date=2017-05-07}}</ref> Despite this, it was rarely used on floppies, particularly because of the cache eating precious space, and because of the limited space preventing a large number of files to cache in the first place.

The ''DirCache''-mode further lacks any mechanism for [[Garbage collection (computer science)|garbage collection]], which means that partly filled cache blocks are never consolidated and will keep taking up space.<ref name=":0">{{Cite web|url=http://wiki.amigaos.net/wiki/DCFS_and_LNFS_Low_Level_Data_Structures|title=DCFS and LNFS Low Level Data Structures - AmigaOS Documentation Wiki|website=wiki.amigaos.net|language=en|access-date=2017-05-07}}</ref>
|-
| colspan="3" style="background-color:#d7dfe4" | '''Note:''' Both ''DirCache''-modes are <u>not</u> backwards compatible with earlier versions of FFS.<ref name="Amiga_OS_3.1_Workbench_FFS-reference_DirCache">{{cite book |author=AMIGA Technologies GmbH |date=1995 |title=AMIGA OS 3.1 Workbench |publisher=Escom AG |quote=Disks using Directory Cache are incompatible with Workbench software releases prior to 3.0 and should not be selected for disks that are also used on pre-Release 3 Amigas. |page=84 |url=https://archive.org/details/EscomAmigaOS3.1Workbench/page/n83/}}</ref>
|}

Version v40.1 was the last version of FFS released by Commodore, and came with AmigaOS 3.1, both on the OS disks and in the ROM.

After this, several [[Unofficial patch]]es appeared which allowed its use on drives after the first 2&nbsp;GB of a hard disk, using a 64-bit addressing system called ''TrackDisk64'' or TD64 (although the [[2 GB limit]] on file size and the 127&nbsp;GB limit on partition-sizes remained, as it was a limitation of AmigaOS' <code>dos.library</code> and all then-current Amiga software) and carried the version number of v44.

The version of FFS that came with the later official licenced AmigaOS-releases from German distributor [[Haage & Partner]], AmigaOS 3.5 and v3.9 respectively, was v45 – It differed from the former versions in that it used a alternate 64-bit addressing system, called ''New Style Device'' or NSD.

More recently in 2003, [[MorphOS]] and [[AmigaOS versions#AmigaOS 4|AmigaOS 4]] have introduced support for a slightly updated "FFS2", by Olaf Barthel (FFS v46, v50 respectively) – This release is compatible with the older FFS. It is [[PowerPC]] native, and introduced further two more DOSTypes:
{| class="wikitable"
|-
! style="width: 5%"| DOSType
! Type
! style="width: 15%"| AmigaDOS
|-
| <code>DOS\'''6'''</code>
| Addition ''Long Name Filesystem'' (OFS-LNFS) for OFS.
Possibility to use long file-names of up to 107 characters for OFS.
| MorphOS, AmigaOS v4.0
|-
| <code>DOS\'''7'''</code>
| Addition ''Long Name Filesystem'' (FFS-LNFS) for FFS.
Possibility to use long file-names of up to 107 characters for FFS
| MorphOS, {{nowrap|AmigaOS v4.0}}
|-
|colspan="3" | → There are no directory caching modes available for the aforementioned ''LNFS'' DOSTypes. ''International Mode'' is still inherited by default.
These modes for implementing [[Long filename|long file-name-additions]] (LNFs), allows OFS and FFS to hold files with a longer filename (up to 107 characters) than the usual Amiga limits of former OFF-/FFS-releases, which is 31 characters.<ref name=":0" />
|-
| colspan="3" style="background-color:#d7dfe4" | '''Note:''' Both ''LNFS''-modes are <u>not</u> forward compatible with earlier versions of FFS, even if the release itself is backwards compatible to former FFS-releases.
|}

However, despite eventually obtaining additional features and ultimately the ability to use the long filenames, by the time these additions were made, FFS already compared very poorly to other available filesystems on the platforms it was available for. Apart from these extra DOSTypes, there are little or no functional difference between FFS and FFS2 (although some older non-specified bugs may have been dealt with) and should still not be used except for legacy purposes. Disk validation is still necessary in FFS2 (and may still result in data loss) just as it was on FFS, despite early beliefs to the contrary.

In September 2018, Hyperion Entertainment released Amiga OS 3.1.4 build upon the Amiga OS 3.1 source. It included an updated FastFileSystem V46 within the Kickstart ROM. The V46 FFS natively supports the APIs for ''TD_64'', ''NSD'', and/or the classic 32-bit ''TD_ storage''-calls. This lets the Amiga OS v3.x use and boot from large media (>4GB) natively, and support >2GB partition sizes.

In July 2019, an additional file-based update to FFS was contained in the 3.1.4.1 update.<ref>{{cite web |url=https://www.hyperion-entertainment.com/index.php/news/1-latest-news/280-update-to-amigaos-314-released. |title = Update to AmigaOS 3.1.4 released}}</ref> In May 2021, an updated Amiga OS 3.2 was released<ref>{{cite web |url=https://www.hyperion-entertainment.com/index.php/news |title = News}}</ref> and provided a matching ROM-based V47 FFS update which gained a few minor features and fixes.