Some file system are case insensitive, other are not. When you try to checkout git repository, it's possible to face this kind of error:
error: You're on a case-insensitive filesystem, and the remote you are trying to fetch from has references that only differ in casing. It is impossible to store such references with the ‘files’ backend. You can either accept this as-is, in which case you won't be able to store all remote references on disk.
Book
A brief and visual description of cognitive distortions.
Blog
Things that you should now about disk IO.
source
Here is a nice example how to use profile guided optimization for Go languange.