> let's think about what a hpc cluster is for. > Second, one should always ask the question where security is to be > applied, +1 You have to assess your environment and weigh up the benefits of uptime vs security. Sometimes the security that is fixed in a new kernel is inconsequential in your environment; sometimes the external security on your network is such that the attack vector is tiny. You make a judgement based on your needs. > > > The physicists and mathematicians who count there need high durations. Yes. I too run HPC clusters and I have had uptimes of over 1000 days - clusters that are turned on when they are delivered and turned off when they are obsolete. It is crucial for long running calculations that you have a stable OS - you have never seen wrath like a computational scientist whose 200 day calculation has just failed because you needed to reboot the node it was running on. > > My decision much on Centos because: > > - free > - Maintaining until the year 2024, > longer than the cluster will live. > And stability ... P.