The BeOS stuff you mention is sort of true, but not really. BeOS once had a full on database based file system, but that's not BFS. The OFS (Old File System - w

The BeOS stuff you mention is sort of true, but not really. BeOS once had a full on database based file system, but that's not BFS. The OFS (Old File System - what they called it with in BeOS) had full on no holds barred database storage. But the performance sucked, synching the metatdata in the file system and database (which were different structures apparently) was a bit flakey, and the base for the way the filesystem worked was incompatible with integrating other file systems in to the OS. Dominic Giampaolo and Cyril Meurillon ended up creating a whole new base for the file system with VFS layer, etc. As part of that the BFS file system was created. This incorperated a subset of what the file system used to be able to do - it had extended attributes (for adding arbitrary data to the file), a query layer to allow querying those attributes and a mechanism for live queries that would allow the data to dynamically update. But it wasn't really a database in the same way WinFS was meany to be - i.e. built on top of SQL Server.