If you want your Hadoop job to begin as soon as a machine is available, you pay the list prices. If you want to gamble a bit and wait for empty machines, the spot market lets you put in a lower bid and wait until spare machines are available for that price. Amazon is experimenting with constantly running an auction for compute power. This is yet another wrinkle for the engineers and the accountants to spend time discussing.
My favorite, relatively new feature is the Amazon Glacier, a backup system that takes hours to recover the data. Many people looked at Amazon's first cloud storage solution (S3) and found it was too expensive for backups or other data that wasn't accessed very often. One-size-fits-all solutions are one of the limitations of the cloud. Amazon designed S3 to meet the needs of servers that must access data relatively quickly.
As I mentioned before, there's no easy way to cover all of Amazon Web Services in one article like this. The only solution is to wade in, start booting up machines, and begin testing your application. Amazon offers some very basic services for free to help new customers, but for the most part it costs only a few cents to try out the different sizes. Then you can sit down with your accountant and start pricing out the services.
My impression is that Amazon's cloud has evolved into the high-end Cadillac of the breed. It provides extensive documentation, more hand-holding, and more sophisticated features than rivals, all at a price that is higher than the competition. Perhaps the competition's rates are only temporary and perhaps they're unsustainable, but maybe Amazon's rate is the price you pay for all of the extra features. Amazon's cloud is loaded with them.
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