Comment by hollander

Many years ago we had a webserver that would stop working every other Friday around noon. I couldn't figure out what the problem was. I was the de-facto systems administrator, just because the previous left, so I was not really into this stuff. It was not a big deal, this was a non-essential development server, so I didn't pay much attention to it. I figured out the server rebooted, and the webserver didn't start automatically after a reboot. This was a configuration problem, and if it hadn't been for this, I maybe never would have known about the problem.

About half a year later we were working in the server room, replacing a server when a colleague unplugged the old UPS in there. Unplugging the UPS for a minute shouldn't be a problem. The battery would take over and nothing would go down.

But well, the two servers attached to it immediately went down. It took me a minute, and then it dawned to me that this was the problem. The UPS did a test every other Friday, shut the power off as a test, which caused the two attached servers to restart, after which the webserver didn't start...

We removed the UPS as we didn't need it in the first place, problem solved.