Addendum:

> Fast File System 2 (FFS) [...] should be the same implementation by Olaf 'olsen' Barthel
> as used in OS4, up to and including DOS\6 and DOS\7 modes (long filenames).

I just read something interesting which was new to me:

"A few years ago I had a go at disassembling FastFileSystem 45.13, the final version released by Amiga Inc. in OS 3.9 Boing Bag 2. [...] One interesting feature I found is code for DosType DOS\8, which seems to be intended to support longer filenames; up to 54 characters vs 30 for normal FFS."
http://eab.abime.net/showpost.php?p=858582

"Enabled and fixed hidden partially implemented long file name support. If partition dos type is DOS\8, max file/directory name length gets increased to 54 characters (from 30) by using previously unused bytes of file/dir header block."
http://eab.abime.net/showpost.php?p=1188826

"DOS\8 is identical to DOS\3 (international FFS) when there are no files with long names. So you can in-place convert an existing DOS\3 partition to DOS\8 just by changing the DosType in the first longword (and edit your mount file to reflect the new DosType). Similarly, you could convert back to DOS\3, providing you're certain that there are no files or directories with long names in the partition. Programs like DiskSalv and ReOrg won't of course work with DOS\8 partitions."
http://eab.abime.net/showpost.php?p=1188965

"DOS/8 was "sort of present" already in the Os 3.9 version, but there not fully functional. It has 54 character long file names (so more than the usual 30), but is backwards compatible in the sense that the block layout is just like the one in DOS/1, except that unused fields are populated with the extra characters, so old tools will at worst damage the file name, but nothing else. Probably we'll keep DOS/8 inofficial, as it used to be."
http://amiga.org/forums/showpost.php?p=833207

"About the only thing that was present of DOS/8 in the 3.9 release is ExAll() and friends, and the computation of the maximum file size. Everything else on file names in DOS/8 was there borken... Open, Rename, Lock, .... you name it. I cleaned this up for V46, so it now works quite fine on my HD since probably a year or so. [...] DOS/8 is most likely not going to become official [...] because we have another alternative that is more flexible."
http://amiga.org/forums/showpost.php?p=833258

"there is one "hidden" feature we do not support officially, and this is DOS\08. Nobody remembers how, but Os 3.9 already supported it, albeit incompletely. It is an FFS variant that supports long file names limited to 54 characters, but that is backwards compatible to the older flavours of the FFS such that you can easily upgrade from DOS\03 to DOS\08, gain additional length, but do not need to reformat. Unlike the Os 3.9 variant, this version works, however. We still do not support it officially as diskdoctor [...] does not support it, but it is otherwise in fine working condition."
https://forum.amiga.org/index.php?topic=73694.msg840687#msg840687


Edit: added one more

[ Edited by Andreas_Wolf 13.10.2018 - 14:40 ]