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Asked: 2026-05-11T11:43:34+00:00

I’m in the process of implementing caching for my project. After looking at cache

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I’m in the process of implementing caching for my project. After looking at cache directory structures, I’ve seen many examples like:

cache cache/a cache/a/a/ cache/a/... cache/a/z cache/... cache/z ...

You get the idea. Another example for storing files, let’s say our file is named IMG_PARTY.JPG, a common way is to put it in a directory named:

files/i/m/IMG_PARTY.JPG

Some thoughts come to mind, but I’d like to know the real reasons for this.

  • Filesystems doing linear lookups find files faster when there’s fewer of them in a directory. Such structure spreads files thin.

  • To not mess up *nix utilities like rm, which take a finite number of arguments and deleting large number of files at once tends to be hacky (having to pass it though find etc.)

What’s the real reason? What is a ‘good’ cache directory structure and why?

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  1. Every time I’ve done it, it has been to avoid slow linear searches in filesystems. Luckily, at least on Linux, this is becoming a thing of the past.

    However, even today, with b-tree based directories, a very large directory will be hard to deal with, since it will take forever and a day just to get a listing of all the files, never mind finding the right file.

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