A short story about power and spark plugs

So I’m building a storage server. It’s got a very nice supermicro x9sri-f-o motherboard with IPMI and it’s got a redundant PSU.

Last Friday I got all the parts together and started tinkering. Upgraded the BIOS and IPMI firmware. Installed FreeBSD, turned the power off at the PSU’s and went home for the weekend.

Fast-forward to monday, and I’m feeling just a little bit lazy and thought to myself “I’m not going to go into the room next door to boot the server, I’m going to boot it via IPMI for fun and profit”.

So I open the IPMI control panel in my browser, and click “power on”. Nothing happens. “That’s odd” I thought “must be an issue with the firmware I updated”.

I glanced at the README.doc and found a difference between the way I updated the firmware. “Doesn’t work without this” it said.

I re-flashed the firmware and waited for the IPMI card to reboot and then clicked the “Power on” button.

Nothing.

“Odd. Very odd.”

I went in to the server to give the power button a push manually.

Nothing.

I looked at the PSU’s. They had power, but was not switched on. Flipped the switches and power came on.

I’m not really sure how that happened, but I figure that the PSU’s have fairly large capacitors on the internal circuit and that had enough power left to keep the IPMI working.

Always check the spark plugs.