I couldn't agree more. Once you're scaling the best thing to do is build purpose built machines tuned to your workload. If you've got a bunch of ruby's running

I couldn't agree more. Once you're scaling the best thing to do is build purpose built machines tuned to your workload. If you've got a bunch of ruby's running and your RAM is at 100% but CPU at 50% you can over spec your web front ends on RAM to fully utilize your CPU. If you've got a DB machine, then you'll want to run 200-500 spindles with another 20 SSDs for indexes per socket and as much RAM as will fit.