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/unused reserved capacity with regional reserved Instance/

unused reserved capacity with regional reserved Instance

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hello everyone, if i bough a regional reserved instance (which gives no capacity reservation in any availability zones within the region) and i created a reservation over a specific AZ match the same attributes of the regional reserved instance and then created the instance in that AZ that match both regional reservation and AZ capacity reservation attributes , do i get charged on demand (no discount) because of unused reservation in the AZ if the regional reserved instance is stopped ?

1 Answers
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Accepted Answer

Reserved Instances cannot be stopped. If you purchase Regional RI, you have it active for the whole term (1yr or 3yr) and can benefit from the discount at any point during that time.

If you use On-Demand Capacity Reservcation (ODCR) in any of the AZ of that same region, the RI discount will apply to resources depending whether you run any EC2 instance inside ODCR or not:

  • if you don't run any EC2 instance inside ODCR, it means than ODCR is unused, and in this case your Regional RI discount will be applied to your unused ODCR (instead of on-demand charges you will be covered by the RI charges)
  • if you have EC2 instance running that is matching attributes of your ODCR, in that case you don't pay anything for ODCR (because it's used), however you are charged for the EC2 instance instead; but because you have Regional RI, in this case the RI discount will be applied to your running EC2 instance, and you will not pay on-demand charges

There's more information about ODCR billing in the docs here: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/capacity-reservations-pricing-billing.html

EXPERT
answered 4 months ago
  • thanks alot i digged the whole ec2 doc and for my question i found answer: for regional RI , if an instance running in AZ match capacity reservation/RI attributes in that AZ if it is running or not i will get the discount ( no ondemand fees for stopping it in behalf of capacity reservation the unused/stoped reserved capacity will be the same as the RI discount) for zonal reservation which apply capacity reservation be default if an instance match the RI stop/unused the reservation capacity will charge me on demand , that strange im new to AWS and was checking how things works thanks alot for your answer

  • Yes, you're right. It seems like you talk about 2 different scenarios...

    • in case with the Regional RI, if you also have capacity reservation (ODCR), then regional RI discount will be applied at any time, doesn't matter if your EC2 instance is running or not
    • Zonal RI cannot apply to unused ODCR; Zonal RIs can only apply to running EC2 instances; if you do not run any EC2 instances, you will be charged the on-demand fee for the capacity reservation;

    Essentially, if you plan to use OCDR, you should rather go with the Regional RI option. Or - better explore Savings Plans instead.

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