It is dangerous to project *your* particular use cases and workflows
upon the community at large.
Most of the clusters I end up building or working on (academic,
government and corporate sites) are intended to support periodic
spikes in computing demands. For university sites this could be the
end of each semester as student projects become due and for research
labs it may be for a 10 day period proceeding the submission of a
major paper or grant applications. For EDA companies entire clusters
may lay idle until some massive validation process needs to kick off.
Clusters built to meet peak demand rarely hit 90% utilization
(averaged over time) and often have lots of idle capacity sitting
around waiting for a peak period to arrive. That is why we pay
particular attention to things like Project Hedeby from Sun and the
EGO stuff from Platform Computing along with the various homegrown
based systems that people have built to power-on and power-off nodes
(via IPMI) based on the length of the pending job list.
In systems built for peak power and not constant throughput power
control is a big deal and the eventual goal I'd love to see is more
grid schedulers and resource brokers becoming hardware aware to the
point of being able to power on and off nodes based on a given policy.
It's coming and I've seen some neat homegrown solutions already.
My $.02 as always
-Chris
On Nov 8, 2007, at 7:02 PM, Vincent Diepeveen wrote:
Building a $2500 cluster in order to NOT run software at it then
nonstop beats the idea of building a cluster. <snip> 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.
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