There is some discussion on /. regarding Linux clustering. Seems the consensus is no book covers this adequately and you're better off using web resources. I concluded something similar from my own research - it seems there is no one guide taking you through the entire process (design, architecture, building and software) and it depends somewhat on your needs.


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Google images
My tip for the day is to visit Google images and search for 'Linux cluster'. Seems people who have built them are keen to display a picture on the web and there is often good associated information.
bioteam
Bioteam (bioteam.net) have a nice collection of their works here: http://bioteam.net/gallery/bioclusters