September 2, 2008: Kill-a-watt
NewEgg is currently selling this handy little device for 18 bucks, plus $7 in shipping. And it’s a great price, but wait, there’s more! Now you can get it for the low, low price of $14 (plus shipping), if you use the promo code EMCAKACAF at the checkout stand. For $21 you can have your very own Kill-a-Watt.
I use my K-A-W when I am setting up a new server. I plug the server into the K-A-W and write down the starting amperage (computers draw the most current at startup, when they power fans at full speed, spin up drives, etc). Then I wait till I hear the fans drop down to their normal, lower speed operation, and measure again - this will be typical of the system’s normal draw. I keep all that data in a spreadsheet, usually sorted by which breaker and/or PDU each server is plugged into. It then becomes easy to see when I am nearing an overload condition.
A problem I have seen in several server rooms is, things work fine until a power outage occurs. Once power is restored, it can be difficult to power the room up again, as all those high starting loads trip the breakers. Similarly, servers draw more power the hotter they get, so if you have any HVAC problems, you can start seeing breakers trip out.
With a $21 outlay and a few more minutes during your server commissioning procedure, you can completely avoid these kinds of issues. There are many other fun and useful things you can do with the K-A-W, like precalculating the power cost per year of a server, or figuring out how overloaded your UPS is. The K-A-W has a readout mode which shows that pesky ‘VA’ number that UPS makers are so enamored of.
It’s a convenient little truth-teller.
