[Beowulf] The Walmart Compute Node?

Vincent Diepeveen diep at xs4all.nl
Thu Nov 8 19:02:13 EST 2007


David,

Building a $2500 cluster in order to NOT run software at it then  
nonstop beats the idea of building a cluster. The reason you build a  
cluster in the first place is to run software cheaper and faster than  
when you would run it on a single node. That assumes you actually RUN  
software and that you have a lack of processing power nonstop. So the  
machines are running all the time. Additionally it's a private  
cluster, not some government type thing.

I tend ro remember the government model assumed in the end 70% usage  
effectively of processing power. That's not real true for private  
users of clusters. You really get far above 90% usage.

So you can argue the idle states do matter in the end for energy  
costs, but you definitely can't assume it's idle majority of the  
time. Building a $2500 cluster in order to then not let it run day  
and night definitely is a thrown away $2500.

Of course one should raise this amount of money a tad to include  
energy costs, or simply use the $2500 including energy costs for a  
year or 3, which seems to be the economic life cycle of a system,  
after which it draws too much power for its performance compared to  
the newer generation cpu's.

Even if we would use the government model of 70% effective usage,  
then the C7 cpu's, arm boards, mips boards and all those 'cheapo'  
solutions always lose it to the power costs, so effectively no one  
who wants a lot of crunching power buys them because of that.

Additionally they're real slow those cpu's compared to intels core2.

On Nov 8, 2007, at 9:54 PM, David Mathog wrote:

> Eugen Leitl <eugen at leitl.org> wrote:
>> It's actually a VIA C7-D. Way worse than a Celery in absolute  
>> performance,
>> but might be okayish to stellar in terms of Ops/Joule.
>
> To expand on the stellar part slightly, if the proposed cluster
> is to be powered on all the time, but won't be in use all the
> time, it's worth noting that the C7 has very low power modes
> which are still running, albeit very slowly.  This would make such a
> cluster quite responsive in terms of starting jobs from the "just
> sitting around" state, without requiring any of the complications,
> overhead, and longish delays associated with returning from
> sleep modes.  In theory the kernel should handle this power  
> conservation
> for you automatically if the cpufreq modules are
> installed and configured properly.  The power consumption when
> the system is sitting around would be minimal, probably just a few  
> watts.
>
> This assumes that the board in question actually supports these low
> power modes.  This is probably NOT a safe assumption for an el cheopo
> board.
>
> Regards,
>
> David Mathog
> mathog at caltech.edu
> Manager, Sequence Analysis Facility, Biology Division, Caltech
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