I'm using MySQL. This is for Net::FTPServer so that when a directory is created/deleted I can recreate the nested set listings as well as the lineage.

For serving the files, I'm using the lineage field so that I can do fast lookups to determine if a file exists on the server. In other words the path ends with a file, remove that and I have a lineage which I can do a lookup on. If I find that lineage then I get the directory ID and find all files in that folder that match my filename. If I don't find it - 404, if I do I continue processing.

A little convoluted but its WIP atm. The concept is that dirs won't be created often but files will.

If it moves to anything, it will be SQL Server.