[Beowulf] Cluster newbie, power recommendations

Charlie Peck charliep at cs.earlham.edu
Mon Mar 20 19:19:21 EST 2006


On Mar 20, 2006, at 6:50 PM, Robert G. Brown wrote:

> On Sun, 19 Mar 2006, Eric Geater at Home wrote:
>
>> Howdy, everyone!
>>
>> Maybe this is a question better suited for hardware heads, but I've 
>> become
>> Beowulf curious, and am interested in learning a hardware question.
>>
>> I have access to a bunch of old ATX computers.  The most likely common
>> processor will no doubt be Pentium II 400, with hard drive space 
>> around 10gb
>>
>> ...
>>
>> This is a power-saving concept... if I could run 16 mobo's on 8 (or 
>> even 6)
>> power supplies, it might be more beneficial to my health and 
>> well-being when
>> the electric bill comes in.
>
> Sigh.  If you do the math, you are better off buying a single AMD64 
> than
> using the whole cluster for "work", especially as far as power is
> concerned.  16 mobos is likely close to 1600 watts -- almost certainly
> over 1000 watts even if you use larger/collective power supplies.
> Compare that to the 100-200 watts for a single AMD64, and you're 
> looking
> at an ~$800/year difference in cost paying for the electricity and
> cooling alone (at an estimated $1/watt/year, which is a bit high
> depending on where you live but probably not even a factor of two 
> high).

I think clusters like the one Eric wants to build have /significant/ 
educational value, both in the building and the use.  How else does one 
learn to do parallel/distributed programming if not on a cluster, even 
a "toy" one?  Sure the single AMD64 will be more powerful but it won't 
provide an opportunity to learn about message passing, speedup, 
efficiency, problem decomposition, etc.

> not the work.  If this describes you, then I'd suggest not worrying too
> much about the power saving right away -- somebody on this list (I can
> think of a couple of folks offhand:-) will likely suggest SOME ways of
> doing collective power, and there used to be a really nice shelved
> cluster on the web that used a single beefy power supply and special
> connectors per shelf of something like 4 motherboards.  Google harder 
> --
> hopefully it is still there (or check the list archives to see if you
> can find a reference, this was a year plus ago).  When they do or you

There are a couple of issues when ganging multiple power supplies, most 
having to do with the lines in the ATX standard where the board sends a 
signal back to the power supply.  I believe the site that RGB is 
referring to is http://joule.bu.edu/~hazen/LinuxCluster.  If this isn't 
enough get in touch, we have worked through these same problems for our 
portable clusters, see http://cs.earlham.edu/little-fe

charlie

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