After some playing with Unslung on my Linksys NSLU2, I realize it was a very limited solution for our needs. We need to share 4 (sometimes 5) NTFS (or others) volumes, where everyone of them is 500GB.
Read it here
So, I came back to the Debian/NSLU2 solution. This time, with all the intention to make it work.
Its quite pointless to report here all the things I did to make it work in the way I want/need.