Well why have downtime if you can avoid it with a bit of work?

But I do agree the poster should think about this. I don't think it's 'off' or misleading, they just haven't encountered a hardware error before. If they had one on this single box with 30 databases and 34 Nginx sites it would probably be a bad time, and yes they should think about that a bit more perhaps.

They describe a db follower for cutover for example but could also have one for backups, plus rolling backups offsite somewhere (perhaps they do and it just didn't make it into this article). That would reduce risk a lot. Then of course they could put all the servers on several boxes behind a load-balancer.

But perhaps if the services aren't really critical it's not worth spending money on that, depends partly what these services/apps are.