[Beowulf] Rack power requirement question

David Kewley kewley at gps.caltech.edu
Thu Apr 14 23:35:31 PDT 2005

Hi David,

David Mathog wrote on Thursday 14 April 2005 11:59:
> For the design of a new computer room I need to put together an
> estimate ASAP of typical power usage by a mythical
> "full computer rack" - 3 years from now. My crystal ball is a bit
> fuzzy in that range

I wonder who has a crystal ball that *isn't* fuzzy in this realm?

> so I thought it best to collect several 
> opinions and then present an answer based on those values. If you
> have a moment please fill in your best guess for power
> consumption values, in 2008, in kilowatts for:
> 1.  a "high end" rack               (most power)
> 2.  an "average" rack               (average power)
> 3.  the "minimum worthwhile" rack   (least power)
> The third one is a probably not named well, so here's an example
> in today's terms: this rack might be stocked with Pentium III's
> from 2001 or so, since anything cooler than that wouldn't
> calculate fast enough to be worth the effort of maintaining it.

The only reasonably easy one, to me at least, is #3. :)  I'd say 10kW, 
assuming around 40 nodes at 250W apiece.  If you don't like 250W/node 
increase accordingly e.g. to 12kW.

Guessing 3 years out?  I don't think the CPU manufacturers themselves have a 
good idea what the power consumption will be.  Will processors keep burning 
more power, or will engineers more squarely face the challenge of reducing 
power or better managing it?  Will future 1U boxes have typically 2 
processors or 4?  Will CPUs be quad-core?  Will 1U's be out & blades in?  
Will blades be out & multi-U supercomputer-in-a-box be in?  Will the Cell 
processor and similar architectures hit mainstream and turn everything on its 

As an example of how invalid simple extrapolation is, Intel will be selling 
around the end of this year a dual-core Itanium (Montecito) that has 1.7x10^9 
transistors and 24MB of L3 cache.  It runs faster than current Itaniums, yet 
consumes less power (not less than 2x, less than 1x!).

I'd guess that any one CPU will be limited around 100W.  I could imagine 4 
CPUs in a 1U box, add another 100W for everything else, and you're up around 
500W.  Times 40U, you get 20kW.  I guess blades are similar even now.

Maybe the high end rack in 2008 will be 25kW?


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