When would you store metadata on a filesystem rather than a database?

I want to store documents with metadata in a web application such that a person can view them in a hierarchy.

I gather that a typical way to do this is to create a database entry for each document, store metadata in the database and store the files on a filesystem.

It seems much simpler and faster to store both the documents and the metadata on the filesystem. So a directory might look like this

$ ls subdirectory
.json
Subsubdirectory
bar.pdf
bar.json
foo.tex
foo.json

And then I could get the metadata from the json files (or whatever format I use). I could render subdirectory/foo.html based on the contents of subdirectory/foo.json. And I could render subdirectory.html based on the contents of subdirectory/.json and the contents of the other child json files.

The main disadvantage I've thought of is that it might be harder to search based on the contents of the metadata file (though I could search based on fil开发者_开发百科esystem-level metadata). What other disadvantages are there? And if people do use this approach, why don't I hear about it?

EDIT: I'm not really so concerned about searching; if I build some sort of searching, it'll probably be within a single, smallish directory.

"I could search based on filesystem-level metadata" - you could do this but it means each time you do a search you have to read all the metdata files from the FS and then you have to manually process it. There's no indexing, this is roughly the equivalent of a full table scan in an SQL database (but it's even slower..).

In general storing data on the FS has some other drawbacks, you have to do replication both for durability (so you don't lose files if the disk dies), and if your site is popupar, for scalability. But since you already storing the files on the disk you have to solve this issue anyway.