1. Mount options: use noatime Most Linux server machines can do without last access time modified for every file and each directory which is being read. So I'll just go ahead and re-quote for the nth time what Linux Kernel developer Ingor Molar has to say to emphasize the point.
i cannot over-emphasise how much of a deal it is in practice. Atime updates are by far the biggest IO performance deficiency that Linux has today. Getting rid of atime updates would give us more everyday Linux performance than all the pagecache speedups of the past 10 years.