Um, I'm not entirely sure what you mean, but I'll try to respond as best I can.

In a general sense, yes this cluster is going to be used for data processing. Specifically, I'll be allowing a friend of mine who likes to play around with a Open Source 3D app called Blender to use my cluster to render his work, leaving his regular PC free for other tasks.

I'm not qute sure what you mean by "data storage is a better idea for make and implemment a cluster scheme or not", but if you mean a Storage Area Network (SAN) instead of a data processing cluster, then the answer is no I won't be using this for storage.

Oh, and just so people who might be interested know, the machines on my cluster will be rather old clunker servers, salvaged from a company I know that was going to toss them in a dumpster (I have an inside source who let me know BEFORE they actually ended up there).

EDIT: I almost forgot, I don't actually HAVE a security project to use on my cluster. I'm LOOKING for one - I'd like to try and contribute what I can back to the security community at large.