eljefe6a writes: "Putting some numbers and data behind the Hadoop hype took a few months of research. I ran 1, 2, 3, 4, 5, 10 and 20 node Hadoop clusters using Elastic MapReduce to check its scalability. As expected, Hadoop scales very well. I also run performance tests on EC2 instances. Then, I break down the ROI of Spot Instance market and cost per unit." Link to Original Source
Computers are unreliable, but humans are even more unreliable.
Any system which depends on human reliability is unreliable.