Energy-hogging Linux, what to do?

[blu at vl.com (Tom Metro)]

Rich Braun wrote:
> Want to find out how much your nice new Linux server will cost in annual
> electricity consumption, before you buy it?  Sorry, you can't:  no
> manufacturer anywhere posts energy consumption information.

True. I recently noticed an advertiser in Linux Journal Magazine, Poly 
Systems (www.polywell.com), promoting a 1U "Power Saving ISP Server." 
Yet they don't list any specific numbers in the ad or say to what extent 
it saves power compared to other systems, or even explain how it saves 
power. The specs they do list seem pretty typical: AMD Semperon or 
Opteron CPU, 512 MB RAM, 80 GB drive, etc.


> A little googling leads me down the path of...DC-to-DC converters
> that run on 12V instead of normal 120V PSU's.

Can you elaborate on that and cite a reference?

I know DC-to-DC converters is/was a popular way to go for telecom 
equipment, but the justification there was that any equipment designed 
to run off of the in-house 48 V battery voltage would gain the benefit 
of continuing to run during a power failure.

This approach isn't likely to be practical unless you're dealing with 
racks of machines.

Consider that the most power hungry component in your PC - the CPU - is 
already running off of a DC-to-DC converter on the motherboard. (That 3 
V output from your power supply is essentially wasted these days, with 
CPUs instead drawing from the 12 V line.)

I suppose you might gain something by investing in one high quality 
(with power factor correction), high power (500 W) supply, and using it 
to run 2 or 3 machines. Newer power supply designs with modular 
harnesses might even make that reasonably easy to do.


> we Americans happily plug all these things in without a thought...
> ...ignoring the $200 we'll spend each year...

Time for EnergyStar ratings on computer systems (not just monitors)?


> So my next server overhaul will include low-power motherboards...
> 
> Have any of y'all built low-power or solar-powered Linux servers?

My last set of servers I built were what I called "micro servers." The 
goal wasn't power savings, but instead noise reduction and space 
savings. To meet those goals it helps to reduce the amount of heat the 
system generates, which of course directly relates to the power consumption.

The CPUs were chosen to be just fast enough for the task, and not 
overkill, and the power supplies similarly low capacity (efficiency is 
another matter). Even with modest speed CPUs, the first enclosure/power 
supply combination I tried using had inadequate current capacity on the 
12 V line to run the CPUs. Switching to a higher quality case/power 
supply, which had the same wattage supply, but had the current better 
allocated among the various outputs, did the trick.


For servers that require even less horsepower I plan to use appliance 
hardware. I have a Linksys WRT54G awaiting conversion to third-party 
firmware for such a project. Someone else mentioned the Linksys NSLU2 (a 
network attached storage appliance[1] that is capable of running Debian 
Linux[2]), which actually has its 266 MHz ARM processor underclocked to 
reduce power and heat.

[1] http://www1.linksys.com/products/product.asp?prid=640&scid=43
[2] http://www.nslu2-linux.org/wiki/DebianSlug/OpenDebianSlug


> I...have mail-ordered a couple of Kill-a-Watt consumption meters to
> plug my systems and appliances into.

I've often seen those in home automation catalogs, but if you find the 
one you bought works well, please post a pointer to it.

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/