CoreOS performs green/blue deploys of the OS which is consistent with modern thinking. But one thing that is not completely apparent is which folders are supposed to be safe during upgrades? After a recent upgrade to 991.1.0 on the Beta channel I lost 3 of 6 folders in my /media folder. I’m pretty sure that the media folder is meant to hold symlinks or maybe similar to mount points but it’s not transparent.
One other thing that happened in my cluster… It is a common belief that each node should have it’s own haproxy instance. While it’s not clear how it’s supposed to be configured things get a little weird when using etcd, confd, and haproxy as DNS records seem to be aggregated across the cluster. And since some of my services are pinned to one machine things get wonky when the alternate machine tries to setup haproxy for a hostname that does not exist. (in my case gitlab and registry)