I understand the math lesson and how it costs more to add each 9 to your uptime. All that will not help you convince someone who doesn't know these things. Its

I understand the math lesson and how it costs more to add each 9 to your uptime. All that will not help you convince someone who doesn't know these things. Its the difference between a sales ptich and an engineering discussion. Redundancy is a great tool but its not a panacea. You mentioned many of the drawbacks yourself. I see too many people building gigantic RAID arrays with consumer hitachi drives and questionable controllers. It's exceedingly easy to think you're adding redundancy when you are just creating a house of cards.