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Comment by HedgedHuman | Hacker News Reader

Neat! Did not know that. Thanks :-) The 100GB RAM cap seems rather limiting though.

The ideal case scenario imho (one step beyond this stop/start-at-will feature) would be "convertible" spot - being able to migrate to on-demand with zero downtime when ec2 needs that capacity back - that'd solve a lot of my problems.

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You can (effectively) do that already -- just set your spot bid to the maximum you're willing to pay, i.e. the on-demand price.

This isn't actually effective. When there are instance shortages and someone launches an on-demand instance, no matter how high you set your spot bid price your spot instance will still be terminated in favor of the on-demand instance. We run hundreds of spot instances with their max price set higher than on-demand and still see terminations on popular instance types: there are few day-to-day, but periodically nearly all of them are terminated at once. During those situations, if you went to replace the terminated spot instance with an on-demand instance, you'll even get an error stating that they're out of on-demand capacity for the instance type in that zone, so it's pretty clear that it happens when they've completely run out of capacity for some instance type in a zone

Spot on!

Some AZs don't have much capacity for certain types of instances.

Fun fact: An availability zone A for person 1 is not guaranteed to be the same as availability zone A of person 2. AWS mixes them up per account.

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