This is a follow-up to this topic because I continue digging.
Well, tired of all this fragmentation that one of the causes is related to the disk cache wipe by mozilla products when they crash, I found that there is a reported bug on this topic, from... 2001!!!:
https://bugzilla.mozilla.org/show_bug.cgi?id=105843
As looks no one at mozilla would do something about disk cache behavior and, therefore, fragmentation. I started to "flirt" with RAM Disk, even I hate it.
Well, not exactly with RAM Disks but with a system like Google Earth cache. This is: a way to have solid cache file that helps to avoid fragmentation.
And beyond this the only thing I found was something that works like it and this is the freeware RAM Disk utility
imdisk. It creates virtual disks, ram disk actually, that dump all its data to a file after unmount them (if you choose to do it).
I'm just starting to use it but, beyond I could imagine, looks that it hasn't a huge impact on RAM memory consumption, helps to avoid continuous I/O (input/output) to hard disk and is quite fast (it's a RAM Disk, after all).
Anyway, it helps quite a lot to file fragmentation (no fragmentation at all) and is what I was looking for.
Maybe in a few days I change and I drop using it, but here I left this message for your knowledge ;)