[Beowulf] A fairly simple question

[V B Hunt]

I am a total newbie when it comes to clusters and HPC.  At the same 
time, I am very interested in the concept and am planning on building my 
own Beowulf.  The purpose of my Beowulf will be to learn parallel 
programming, learn more about problems that HPC solves well, and because 
I want to ;-)  My question is what is the minimum number of nodes to 
effectively learn programming techniques for clusters?  Just by thinking 
about it, I would guess that two slave nodes and a head node would be 
the minimum; however, I have absolutely no practical experience with 
it.  What are the differences, if any, in programming for a 2-node 
cluster vs. a 3-node cluster vs. a 4-node cluster vs. a 16-node cluster 
vs. 1024-node cluster?  This is assuming the hardware of each node is 
identical to every other node, except for the head node.

Thanks in advance.

Brice Hunt