[Beowulf] scalability of cluster paper

[Paul Johnson]

I am wondering if anyone could point me to a paper on the scalability 
issues of NOWs clusters or
Beowulf clusters using MPI.  Im curious what kind of scalability people 
see for clusters less than 10 nodes. 
Any reference to a paper would be greatly appreciated.  I've been doing 
alot of scholar.googling but
havent found what Im looking for yet.

Thanks,
Paul