I found this response to be fantastic, educational, and I've already bookmarked it for future discussions with people regarding cloud storage - so thanks very m

I found this response to be fantastic, educational, and I've already bookmarked it for future discussions with people regarding cloud storage - so thanks very much for your response. I wish I could highlight it as an "Answer of the Month" - but at the very least, I'll share it with others when discussing the topic. So, perhaps another way of looking at this, is the 11 9s of reliability means that Amazon is providing a guarantee that they will lose at least that many objects, but, for all the reasons that you highlighted, there underlying redundancy mechanism means that there are all sorts of reasons why a catastrophic loss could result in many orders of magnitude lost of data, not only during exceptional events, but just under the normal course of business. I would note that your anecdote about losing "data on a hard drive" isn't as relative at cloud storage levels, because one of the things that has been drilled into my mind by a colleague who works on a cloud system at scale, is they not only assume they will lose a single device, but they also scale so that they can lose (in order), a complete Rack, a complete PDU, and a complete Data Center - and still continue to provide availability to storage. That is, in the normal course of business, they plan on losing data centers, and continuing to provide full availability (albeit, at reduced durability in that event until they restore that data center). Google takes this up a notch, and provides availability in the event that an entire region is lost. Cautious companies can roll their own Business Continuity Plans on top of this as well. What would be interesting, but unlikely, is for Amazon/Microsoft/Google to share with their customer what their actual loss of data was in the prior periods (Say, per year), and then provide a rolling graph of actual loss. Also useful (and almost guaranteed not to be available) - is what percentage of customers lost more than their SLA each month.