Directory indexing

Directory indexing feature improves file access time in large directories or directories containing many files by using hashed binary trees to store the directory information. It is a good way to enable it for example on a web server which has thousands of files in a single directory:

tune2fs -O dir_index /dev/sda3

Directory index will be created for new files but you can regenerate index with:

e2fsck -D -f /dev/sda3