Sorry, no, you are missing the point. Most popular databases cannot exist w/o filesystems. filesystem isn't just files and directories, it's the guarantees you

Sorry, no, you are missing the point. Most popular databases cannot exist w/o filesystems. filesystem isn't just files and directories, it's the guarantees you get on reads / writes / copy / delete / create, the cache behavior, the ownership, snapshots, deduplication, redundancy, compression, checksums, encryption... (obviously, not all filesystems do this, and some databases already can take on some of the functions of filesystem). Databases don't implement those features themselves, but will have to, if they decide to work with bare block devices.