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 <[EMAIL PROTECTED]> 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
[EMAIL PROTECTED]
Manager, Sequence Analysis Facility, Biology Division, Caltech
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