[fuckstick]

> But yes, on top of that, there's the question that in the end even the DB will need something very, very much like a filesystem between them and the storage hardware

So the answer to this question is no. The “filesystem” that a relational database uses - ie how it organizes and allocates on the block layer is so different from the DOS/POSIX semantics that you wouldn’t recognize it as a filesystem - so to say it is very, very much like a filesystem is dubious.