AWS Request Spot cost and diversified strategy?

Question

Amazon Web Services

Hello. I’m sorting out the cost in the Amazon request spot and I just can’t understand if this is really so or somewhere a catch. Let's say I add an instance to the fleet that costs $11 per hour, then for the sake of experiment I add all the instances from the list that are less than $11 and I get a cost of less than $1 per hour. So it turns out that I can buy out just huge capacities for pennies, which will cost like one seedy ordinary ec2 instance?
And the second question, I read the docks for a long time, googled a lot, but I still don’t really understand how their new "diversified" strategy works in the "Fleet allocation strategy". What is the difference between 1 and 20 if I can just set it to All? And in general, what is diversified that the lowest price does not affect the approximate cost of $ per hour.

Answer 1

What exactly is the difficulty? You pay separately for each spot instance, so it is not possible to downgrade one spot at the expense of another. It is, in fact, just a cost calculation algorithm.
As for allocation, everything is simple here - this is an algorithm for distribution over pools and there is no all option there. The algorithm divides either by cost by pools, or randomly, or as indicated