John, I needed to regurgitate the basic Unix desugn for exams - have not kept up with those you mention - had no real need at the time they first emerged.

The original UFS concept was built on a 'tree structure' which had 'i-blocks' (these COULD be stored consectively - not really a FAT, but similar, but with different data therein) and 'data blocks' of varying chunks - this allowed small files to occupy a very small space, and larger ones to have bigger chunks assigned. There was no need to have these data chunks adjacent, especially since this was all normally handled by the 'DOS' out on the drive I referred to above. Indeed, there are many similar concepts involved in handling the 'Virtual RAM' in main memory... creating, allotting, linking, disposing...

But each file system design works well only for certain patterns of access...

I suppose I should use my spare time to start tracking down the basics of these new Linux FSes... hmmm, there is a start with Wiki, I see...