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I purchased an Amazon EC2 instance at lower cost than regular on-demand instances. When I start a new instance in EC2 there's no indication that I would be using the reserved instance. How can I make sure that the instance I'm using is the reserved instance instead of the on-demand one?

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up vote 11 down vote accepted

AWS automatically charges you the reserved price as long as your used count is less than the number of reserved instances you have.

In other words, there's no distinction between the types, it's purely a matter of accounting, a matter which AWS handles for you automatically.

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You're going to see it on the account activity. You'll have to analyze it yourself but if you know how many instances you purchased and how many are running you can see if you're getting charged what you think you should be getting charged. I purchased a few instances awhile back myself and I wanted to make sure I bought the correct reserved instances so I printed a copy of the account activity and waited a few days and compared the results.

You'll see they have a note saying "reserved instance" on the account activity screen but this is there regardless of whether or not its being used because with reserved instances (heavy usage only) they charge you in advance at the beginning of the month for the whole month. Just make sure your normal charges don't show up and you know that the reserved instances are being used correctly.

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I found a python script that does the work for you:

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Welcome to ServerFault. It's generally encouraged to provide more information than just a link. You might want to edit your answer accordingly. – Katherine Villyard Jan 10 '14 at 22:14

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