The BeBox and BeOS have been one of the most impressive projects of their time. The speed and responsiveness of that operating system is still unequalled in my point of view. Among the really cool features was the underlying file system (Be File System, BFS) which allowed for instantaneous searching, a feature I am still waiting for on Mac OS X.
Dominic Giampaolo is the author of that file system and once wrote a book on it: Practical File System Design with the Be File System. As this book is out of print now, the author has published the book in PDF. His home page states that Dominic is working for Apple now – in the file system group. So there is hope.