Building a (very) low cost cluster

So, with hardware prices continuing to fall and ignoring labor expenses, how cheaply can a small cluster be constructed? Let’s build a “garage cluster” for use at home. (Not everyone needs a cluster at home, but having one can be quite useful.)

First, you have to purchase the hardware. Usually, it’s best to have completely homogeneous nodes: all of the machines should have the same processors running at the same clock rate, the same amount of memory, the same network interfaces, and so on. Additionally, choosing upgradable components can provide an incremental upgrade path.