[Beowulf] What is a "proper" machine count for a cluster
john.hearns at streamline-computing.com
Thu Mar 15 01:24:32 PDT 2007
Mathew Shember wrote:
> Hello all,
> I am just wondering what is a reasonable amount of computers to allocate
> for playing around.
> I was thinking 4 pentiums with dual gig processors. Ram would be a gig
> or more.
Matthew, if I may put some words in your mouth what I THINK you are
saying is that you have some surplus desktop machines which you can
repurpose as a Linux compute cluster (Beowulf).
The list is here to help you, and it will be an excellent
Look at the Cluster Live CD which was recently linked ot on the list.
Designate one machine as the master, and boot the rest off it.
Then look at Rocks and Warewulf.
However, your question is about "what is a reasonable amount of
computers". That actually depends on your job load and more importantly
If you are doing serial jobs which use one machine, your cluster will
scale, so the amount of useful work you get out goes up with machine
count. We assume here you have enough RAM per processor.
However, for parallel work you have to have a fast interconnect.
I assume these machines have gigabit? Even if they have,
I would suggest buying some Intel PCI gigabit cards, they are very
cheap. Put these in and get a decent quality gigabit switch to use as
the parallel network.
Now comes the pitch. The "sweet spot" in cluster nodes at the moment
seems to be a dual socket, dual core Opteron or Intel machine with 2
gigs of RAM per core, so each box is a 4-way SMP
(I will be flayed alive by the list for such cavalier numbers).
Now, such a box is likely to have oodles (scientific term) more
processing power than four pentiums.
So I guess what I would say is - follow the learning curve which many
folks here have done. Build that Beowulf with the four machines, get
your code running on it. Download the evaluations of commercial
compilers - that's an important part of Beowulfery too.
But next year, show the cluster to your bosses and get the budget for a
cluster assembled and delivered by your friendly integrator. The
"cluster" may be as small as one multi-core box of course.
The learning and real work you do with the four-box cluster will stand
you in very good stead when speccing out a bigger solution.
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