Managing reserved Amazon EC2 instances

Question

I'm writing an app and had been paying an hourly rate for my EC2 instance, as I've needed to test. I decided I should just pay for a reserved instance to save money in the long run, but now that I have one, I'm confused about how I'm supposed to manage it. In the "Instances" section of the EC2 management console, I can see the instances that I've launched in the past, and I can stop/start them as I see fit. However, it seems the only way to view my reserved instance is to use the "Reserved Instances" drop-down, but this only seems to let me view them, but nothing else...

So, my question is, how can I do the same thing with my reserved instance(s) that I've been doing with my hourly instance(s)? I basically just want to associate my elastic IP with my reserved instance and install my server image on it.

Thanks!

Answer 1

I believe people are commonly confused by this. In EC2, Reserved Instances are the same as On Demand instances. They show in the same section, they power on/off the same, etc. The reservation is mainly only relevant when it comes to billing.

These documents describe how Capacity Reservations work with On Demand instances.

Basically, you create a reservation for a certain amount of time. During that time frame, if you have an EC2 On Demand instance running that matches an available Capacity Reservation on your account, then your billing will not incur the hourly (or secondly, depending on instance type) fee for the On Demand instance. If you change that instance to a type that does not satisfy the reservation, such as upgrading a t2.large to an m4.large, then you will immediately begin being charged for the new rate of the m4.large.

If you're looking for a method to help with reporting of Reserved vs Non Reserved compute resources on your account, I've found that the Billing and Cost Explorer console is very useful for this. If you are being billed for EC2 compute hours (you will still have EC2 bill for things like EBS, data, snapshots, ELB, etc) then you have compute capacity on your account that is not reserved.

You can leverage the AWS CLI to pull numbers for your reservations, and quantities of instance types that you have, and do comparisons.

• describe-capacity-reservations docs - And here is an example
• describe-instances docs - And here is an example (will need some molding to your language of choice, or CLI)