[CentOS] Fastest way of removing very large number of files?

Hi All.

I currently have a problem on my backup server with very large number of
small files in a large number of directories. I would like to delete them
as fast as possible. Currently I use:

rsync -a --delete /empty_directory/ dir_to_clean/

I've read that rsync will be faster than rm or find.
Can you recommend something? I use an ext4 filesystem.

Best regards,
Rafal.