I don't think you comprehend the term "clustering" and how it works in practice. Now I think you are asking about taking something like 4 or 5 old PCs and making them 1 virtual PC. Not possible and you need extra hardware anyway. The CPUs have to share the same storage component for that. Meaning a RAID box or some other external device. In addition the clustering software has huge overhead. It's hard to do and prone to critical failures until everything gets worked out. I haven't built a linux cluster but I have built MS Active/Passive clusters. They are too complicated to be practical in most cases. Meaning cluster failures are extremely hard to recover. I sometimes wish I just built separate boxes and ghosted them vs a cluster. But that's MS eh?