Filesystem optimization?

What this article makes me interested in is doing the same for traditional
hard disks. You could make an extension in ext4 that will reserve some
space for sReadAhead which contains only the useful parts of files and a
special index that says what data is in there. If ext4 will read during
boot time that index and the subsequent data you would have read all data
needed during boot and io would no longer be an issue.