Buy a turn-key system and start working right away. This option is usually the most expensive in terms of initial cost, but you are guaranteed a working system.”

Doug, I agree with everything you say, except this:

Buy a turn-key system and start working right away. This option is usually the most expensive in terms of initial cost, but you are guaranteed a working system.”

That’s only true if the cluster vendor sets it up the way YOU want. I’ve seen a few clusters where the cluster vendors sets things up the way THEY want, so you get a working system, but it doesn’t work they way you need it to.

Just the other day, I was working on a cluster from a well-respected Linux Cluster vendor, and I found a facet of the configuration from the vendor that I found to be ridiculous for a cluster, and it was causing problems. In other words, it wasn’t working. I couldn’t fix it, b/c that would mean taking the cluster off-line, and would (probably) break plenty of other things. In the end, the user had to work around this problem.

So we paid for turnkey system from a true cluster vendor and it still didn’t work correctly.