On Nov 9, 2007, at 1:27 AM, Chris Dagdigian wrote:
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
A few remarks:
a) the 70% usage comes from "supercomputer report europe".
b) "the community" that posts here has like NEAR TO ZERO $2500
clusters at their work,
so if you happen to know 1+ then that already gives statistical
significant bragging rights.
Ever seen a company say: "heh here you got $2500 build me the fastest
cluster you can get for that money"?
Actually i'm typing at an ex-company machine, a macbookpro 17'',
which i got from my previous employer and it is still 2600 euro in
the shop here, which soon is a dollar or 5000.
In general when crunching becomes important to a company, definitely
a billion euro company, then they're gonna invest quite some more
than $2500 into crunching power.
c) homegrown clusters usually are not built at the same manner like
the $2500 project says. Usually people buy a machine now, buy one a
year later and so on, and just cluster 'em, so instead of trying to
stick strict in some $2500 budget it's more like: "which cpu at what
cheapo mainboard gives most dang for my bucks". that'll be a quadcore.
d) for $2500 private clusters (private as in: at home) energy costs
play a big role.
e) another result of increased energy costs is of course sound concerns.
Regarding C: A far more interesting theoretic question is of course
whether you should see most homegrown clusters as a cluster or as
some jbon (just a bunch of cheapo nodes), as i can't really recall
most 'private house clusters' to have even MPI installed. When is it
a cluster?
heh you sure you still want your 2 cents in dollar currency rather
than euro's?
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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