[Beowulf] /. Cooler room or cooler servers?

Mark Hahn hahn at physics.mcmaster.ca
Mon Apr 11 22:05:28 PDT 2005

> > Scuse me?  Our Dell PE1850s come with (dual-capable) 550W power supplies, yes, 
> > but in our configuration, a Dell engineer used a Dell configuration tool to 
> > calculate that the maximum POSSIBLE power dissipation was 361W.  The 
> > implication was that typical max power dissipation would be a fair bit below 
> > that.
> Do you know if its possible to get that configuration tool from somewhere?

HP has similar power-calc spreadsheets available.  really, it's not rocket
science, though it certainly helps to have the power specs all in one spot.

you can get them yourself, though.  for instance, a dimm counts as only
a few watts (say 3-5).  a disk is 10-20, depending on activity, flavor, etc.
power supplies are roughly 75% efficient.  interconnect power is quite 
modest (say 5W).  CPU dissipation varies widely, but is not that hard to 
get, approximately (60-90W for amd, quite a lot more for Intel).  amusingly,
a high-end graphics board can easily be the hottest component in a system,
though not often used in clusters...

don't trust vendors too much.  certainly don't build your system based on the 
max power spec of the power supply

personally, I don't think it makes that much sense to sweat the power
past +=20%.  I designed my current machineroom for 512 300W systems (a year
ago), knowing that real 1U duals dissipated around 220 at the time.  I'm very
happy that AMD has done such a good job on power, since I'm getting 768
instead ;) 

my advice: sandbag by at least 30% and get a kill-a-watt.

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