Read ahead is a kernel level parameter; having tuned it before (also for a Cassandra ring) I would not expect to have to restart any user level processes for it

Read ahead is a kernel level parameter; having tuned it before (also for a Cassandra ring) I would not expect to have to restart any user level processes for it to take effect. But the real issue is understanding the platform that you are building on, and having the tools to explore how that platform works. I am so thankful that Brenden is out there doing this work and sharing it for the rest of us to benefit from!