[lelanthran]

> Conversely, filesystems are often implemented using B-trees as many RDBMSes are but aren't designed for many of the operations one might typically ascribe to a database.

Filesystems are not a relational database, sure, but the word "database" in the context of computer systems, computer science, IT and technology in general doesn't mean "relational database".

Filesystems are definitely a hierarchical database, which is different to a relational database.