Now that we’re in 2009, it’s been a few years since we’re more and more aware that energy is a valuable resource that should be spared. Where I work I’m handling a medium-sized datacenter of 160 servers, and they use approximately 28 kW of power. 28.000 watts, that represents 2800 LED light bulbs, always on, burning day and night.

To this, we can add the cooling system’s consumption, which we don’t monitor but we can safely add 3 to 8 kW for the three cooling units, depending on the outside temperature. That’s what fun about datacenters, we have to burn electricity to cool down the room heated by the servers’ electricity consumption. Consider it the equivalent of putting the oven in your fridge when you bake a cake.

We’ve been trying to minimize a bit this consumption. There’s an article there that writes about shutting down servers when they’re not in use – ie, at night, or during the week-end.

Well, we thought of it first ! :-) In my opinion, it isn’t possible to shutdown every server at night : the backups run during the night, and saving its data is much more important to a company than saving electricity – sadly in some sense… So, we can’t shutdown production servers with important data on it. Luckily, where I work, a very large part of the datacenter is used for development and testing – we’re doing cluster-oriented storage, we have clusters, and about 140 out of our 160 servers are completely unused at night: developers go home.

So, one year and half ago already, I’ve implemented a way for developers to tell whether their test servers could be shutdown at night or not (in case they have long-running tests on them). It’s not a huge success, mainly because people choose 24/24 instead of 12/24 “just in case”, I think, but with approximately 30 servers down every night and during week-ends, we still spare 8 kW more than half the time (96kWh every night). Still better than nothing…

Besides, at home, I’m now putting my laptop to sleep when I’m not in front of it. The saving’s much less and completely nullified by the server in the cupboard, but it’s still better than the days where I had three servers in the cupboard and didn’t put my laptop to sleep !