Details for modifying a reserved instance

Question

I'd like to modify our reserved instance from to a larger instance in the same class. Importantly, it is a convertible instance and I am able to find the documentation regarding how to modify the instance. However, I am not seeing the technical details of what that entails.

Do I need to disconnect the EBS drives currently attached to my reserved instance before proceeding with a modification?

Does a modified reserved instance just automatically appear and all drives, users, settings, etc move to it? Or do I have to reconfigure the new instance with my original instance's settings?

Answer

If it's within the same instance family (T4, M5, etc) and you are just changing size, you shouldn't need to do anything special:

From the docs [Instance Size Flexibility](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/apply_ri.html#ri-instance-size-flexibility):
> With instance size flexibility, the Reserved Instance discount applies to instance usage within the instance family. The Reserved Instance is applied from the smallest to the largest instance size within the instance family based on the normalization factor.

When changing out the instance resource itself, you will want to ensure you preserve any resources that may be destroyed along with the instance such as ENI, EBS volumes, etc. You can then re-attach these resources to the new instance.

Details for modifying a reserved instance

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