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

Lux, James P james.p.lux at jpl.nasa.gov
Wed Jan 21 19:56:27 EST 2009




On 1/21/09 12:10 PM, "Robert G. Brown" <rgb at phy.duke.edu> wrote:

> On Wed, 21 Jan 2009, Lux, James P wrote:
>
>> 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..
>
> But often you can't get "cheap" industrial space.  You need excellent
> climate control and server-room class wiring.  Otherwise you can add the
> cost of outfitting it with a couple of Lieberts, a harmonic-balancing
> transformer, and a rewiring job (amortized however).  Call it a few
> hundred thousand over N years?
>
> In server-class space, this is all provided but I doubt you'll get away
> as cheaply as all that -- after all each node costs THEM an amortized
> chunk of that same set of Lieberts and transformers.  Also, may server
> rooms offer "management" services -- somebody onsite to e.g. reboot your
> nodes or babysite the power and AC while you sleep.  This too adds cost.
>
> So I think your estimate above is a lowball -- not implausibly low for
> space that is "free" but you pay for power, but I'm guessing low by a
> 500-100% for a space you can just put your nodes in and not worry about
> them (adequate space, security -- you've got tens to hundreds of
> thousands of dollars of hardware in there and may have valuable data as
> well, adequate AC and power, and maybe a systems admin qualified
> babysitter.
>

Sure, it's lowball, but even if you multiply by 5 ($5/sq ft), it's still
less than the utility costs...

And, really, the question originally was whether in 3 years you've paid as
much for infrastructure and utilities than you did on the box, and I think
that it's certainly in that area.



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