Image upload storage strategies

Question

When a user uploads an image to my site, the image goes through this process;

• user uploads pic
• store pic metadata in db, giving the image a unique id

Answer 1

MediaWiki generates the MD5 sum of the name of the uploaded file, and uses the first two letters of the MD5 (say, "c" and "f" of the sum "cf1e66b77918167a6b6b972c12b1c00d") to create this directory structure:

images/c/cf/Whatever_filename.png

You could also use the image ID for a predictable upper limit on the number of files per directory. Maybe take floor(image unique ID / 1000) to determine the parent directory, for 1000 images per directory.