Starting Out with HBase - HBase Design Patterns - page 12

Spot instances
In addition to an on-demand instance, Amazon features what are called spot
instances . These are machine hours traded on the market, often at one-tenth the
price. So, when you are ready to launch your instances, check the Request spot
instances option, just as I have done in the following screenshot:
Here are my savings—the m1.xlarge instance costs 48 cents an hour when
purchased on demand, but its current market price is about 5 cents, about 10 times
cheaper. I am setting the maximum offered price at 20 cents, and that means I will
be paying the fluctuating market price, starting from 5 cents and possibly up, but
not more than 20 cents per hour.
I do not delude myself; I know that the big fish (that is, the big EC2-based
companies) are hunting for those savings, and they apply sophisticated trading
techniques, which sometimes result in strange pricing, exceeding the on-demand
pricing. Be careful with the maximum limit you set. But for our limited purposes of
practicing cluster construction, we should swim under the belly of the big fish and
be just fine.