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I'm surely not suggesting that patching is optional. There are very solid reasons for doing this that still make it a requirement. I'm simply suggesting that (especially early on in your Hadoop journey) you rethink how this process will occur on the hosts that make up your Hadoop cluster. The very obvious easy answer is to simply take an outage by stopping all Hadoop services, perform the OS patching as it is done today, and then restart all services thereby ending the outage. In most shops, this could happen in a very fast manner, but it still requires a service outage which we all want to prevent if possible.
Up until now, my strong advice has been to only apply OS level patches & updates when performing a Hadoop platform maintenance activity such as an upgrade. The intention is to take advantage of the downtime that will be present with an upgrade and, in fact, to encourage platform architects to always be thinking about the next upgrade; especially with the level of innovation (and fixes!) that Hadoop is still undergoing.
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