How do 'RI-Unused' and 'Recurring Fees' differ when it comes to the reservation and utilization of cloud resources in services like AWS?

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• CloudHealth

Issue/Introduction

Reserved Instances (RIs) and Recurring Fees are two different concepts related to the reservation and utilization of cloud resources, like those offered by AWS. Here's how they differ:

1. RI-Unused: This term refers to the amount of Reserved Instance capacity that has been purchased but not utilized.  For example, if a Reserved Instance is purchased but does not run an instance that matches the Reserved Instance specifications for some of the time, they will have RI-Unused.  Essentially, RI-Unused is the wasted capacity that the customer has paid for but is not using.

2. Recurring Fees: These are the periodic (typically monthly) payments that are incurred when either the "Partial Upfront" or "No Upfront" Reserved Instance payment options are chosen. These fees are part of the contractual agreement for the reservation, and must be paid regardless of whether the the Reserved Instances are utilized.

In essence, RI-Unused is a measure of inefficiency - it shows how much of the reserved capacity goes unused.  Recurring fees, on the other hand, are a payment obligation that arises from the chosen payment model of the Reserved Instances.