You can take the metaphor further and use:

/datadir/key1/key2/key3/key4/.../file
[download]

If you look at most high capacity mail routers (if you have linux, you have one of these) they use a similar scheme, with an index to get to the files quickly. There are people around who are doing mini-projects to have database-backed file systems, and file system databases. Expect an explosion when the hurd is released and there really is no difference between a file system and a database.

Certainly this would be your most efficient choice for sorting a huge volume of information, if you have a good file system to do it on.

There have been some hurtful words bandied around about file system databases vs. real database backing for different applications. I don't have links to the nodes but there are some interesting discussions about the best choice for a mailer, etc.

____________________
Jeremy
I didn't believe in evil until I dated it.