Great article. My two cents - I think when you're deploying and managing you cluster it can be really useful on a long term to configure it through through software. By that I mean Ansible or any other similar tool one might prefer. It might be easier to setup each node hands on but consider the example where one of your SD cards in one of the Pi's gets broken after a while, you have to perform the steps again to repair the node. Or if the list of commands you need to perform on each node is really long, it's really impractical because most of the time you're gonna forget something and scratch your head for too long. Primarily for this Ansible and similar tools were developed and considered best practice