noatime

Linus says: "'noatime,data=writeback' will quite likely be *quite* noticeable (with different effects for different loads), but almost nobody actually runs that way."

Well, if you need it, you really need it. Otherwise, why would you ever care? I also don't believe in this 10% number people are spouting. How much it effects you will be determined by how many files you access. I think that should be fairly obvious. I've worked on systems that would crash after just a few minutes without noatime. Yikes!