One day, the shared mount on a ton of systems around the company just stopped working. The master node (these have internal redundancy at the network, controller, shelf, and disk level) had failed over to the redundant node, which after time had so many disks fail without being replace that it went down hard. They had to work with NetApp support (at great expense) to get it back up, which took a few days. The system had been attempting to warn the admins as best it could of the impending doom for the better part of a year, and no one noticed.
The moral of this story is that you can have big-dollar redundant systems, but if you don't also have some dollars going to the care and feeding of them, it's wasted. The other lesson here is that such systems don't exist in isolation and are only as good as their weakest link, which in this case was a now-unreachable SMTP server. Lastly, although the LCD displays were trying their best to also signal this fault condition, people who would walk by these physical machines were used to this, so they didn't bother to actually read the errors. Do that at the peril of anything dependent on that system.