A filesystem isn't so different from a database in the first place. Not really relational, but still. The olde PalmOS had databases as primary storage. Though

A filesystem isn't so different from a database in the first place. Not really relational, but still. The olde PalmOS had databases as primary storage. Though databases seem to have had capacity for blobs, since apps themselves were stored that way, aside from text files, images and whatnot. In fact, afaik some mainframe OSes were built around databases.