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# [Beowulf] RE: Capitalization Rates - How often should you replace a cluster? (resent - 1st sending wasn't posted ).

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Lux, James P james.p.lux at jpl.nasa.gov
Wed Jan 21 06:33:03 PST 2009

On 1/20/09 10:04 PM, "Mark Hahn" <hahn at mcmaster.ca> wrote:

>> Think about it: if you pay 1/3 the cost of a new node per year in rent
>> and utilities,
>
> that seems amazingly high to me.  I don't have much sense for rent,
> but even if we ran our clusters on "retail" power rates it would only
> amount to 2.3% of purchase cost.  you could pretty easily argue that
> our purchase prices are high, but even so still < 10%/year.  with your
> kind of costs, wouldn't it make sense to consider a colo site?  from
> a cursory grep of the web, it sounds like they're still substantially
> less than 33%...
> _

Without going into a big research project.. Here in Southern California,
rents are about \$1/sq ft/month for cheap industrial space. Electricity is
about \$0.20/kWh (maybe for a big bulk consumer, it gets down to the
\$0.10/kWh range)

Figure a node draws 400w, and you can stack 20 nodes in a rack, which
occupies 10 square feet (need to have room to stand in front of the rack,
etc.)

So each node is costing \$144/20= \$7.20/yr in rent and 0.4*8000*0.2 = \$640/yr
in electricity.

The rent is tiny compared to utilities.  \$2K/node seems plausible (3*
utility cost), but that doesn't include any of the infrastructure costs
(racks, cables, installation, copies of Windows Server edition, etc.).  If
the real power draw is more like 200W, and you don't run them 24/7, then
you're getting down to the \$100/yr/node costs..