Powering Your Server

Power is an issue for all non-trivial servers. It’s also tied up with location and remote management.

An ideal server would use zero power and be totally silent. If that was possible, remote management would be a much smaller issue, because there would be less need to put it somewhere else, but not where it will annoy people.

It’s a truism that all the electricity that goes into your box eventually becomes heat that has to get out of your box. That’s why machines have fans. The parts inside heat the air inside, and the fans move the hot air out and fresh, cool air in. The fans also make noise, annoy people, and being mechanical, fail, which lets your box overheat and maybe die.

So there is a premium to be placed on not generating the heat to start with so fans are smaller, quieter, and perhaps unnecessary. Some great links for background reading on this issue is to google “quiet PC” or “silent PC” and “home theater PC”, which address the issues of not generating heat, dealing with the heat by fans, and dealing with the noise fans generate.

Electrically generated heat is also a money issue. In the engineering sense, energy is money. Electricity at my house costs US$0.12 per kilowatt-hour. A 100W PC running for ten hours costs one kW-Hr, or $0.12. Left on continuously for a year, that cost becomes 365*24 = 8760 hours, and that costs 876 kW-hours, or US$105.00.

If I could design a server which used less power, say 50W instead, then the cost per year for electricity would be US$52.50, and I would be economically justified in paying $52.50 more for the parts.  And the second year, I’d be US$52.50 ahead by doing this.

Not only that, the 50W version might be cool-able with a smaller, quieter fan, and therefore less annoying to be near.

There is a whole subculture of enthusiasts for low-power, low noise computers. Often this niche can be found by searching for mini-ITX form factor PC motherboards. Some of these can be entirely cooled by natural convection, which is a way of saying “no fan needed”.

I’ll expand on this later, but some useful things to consider are:

Watch the “TDP” power rating of your processor. You can get CPUs with much lower power. These are lower performance, but high speed CPUs are NOT needed for most home servers.

Watch the power rating of your disk drives. In general, desktop 3.5″ drives are 6W, and 2.5″ laptop drives are 1W – 2W; however, desktop drives have about 2:1 bigger storage than 2.5″ drives, and cost less per GB. The tradeoff gets complex, and so you need to know how much storage you need, versus what power it takes to provide that many bits, and how much you’re willing to spend on electricity, and how much noise you will tolerate.