There are three operations that Moodle performs regularly. They can either be run using Moodle's internal routines coded in PHP or, alternatively, by native versions of each function provided by the host operating system. The second approach is significantly faster as it reduces the load on your server, but is only supported in Unix environments. The three programs that can be run using external programs are:
Zip (for compressing files)
This will accelerate backups and manual zip operations.
Unzip (for uncompressing files)
This will accelerate restore and manual unzip operations.
Du (for listing directories)
This will accelerate the displaying of directory content, especially if it contains a lot of files.