How many files can I put in a directory?

Question

Does it matter how many files I keep in a single directory? If so, how many files in a directory is too many, and what are the impacts of having too many files? (This is on

Answer 1

It really depends on the filesystem used, and also some flags.

For example, ext3 can have many thousands of files; but after a couple of thousands, it used to be very slow. Mostly when listing a directory, but also when opening a single file. A few years ago, it gained the 'htree' option, that dramatically shortened the time needed to get an inode given a filename.

Personally, I use subdirectories to keep most levels under a thousand or so items. In your case, I'd create 256 directories, with the two last hex digits of the ID. Use the last and not the first digits, so you get the load balanced.