> A tree-based file-system is optimised for doing a search from the users perspective, finding a file takes log(files) steps and finding related files is trivia

> A tree-based file-system is optimised for doing a search from the users perspective, finding a file takes log(files) steps and finding related files is trivially cheap. It is likely hard to outdo that with a relational model. A tree structured file system is effectively conflating an index with relations. Another way to look at it is that most FSes are like databases which only allow one index, and expose the index to users.