Why is the Optimizer over-recommending RDS reservations?

Products

• CloudHealth

Issue/Introduction

For RDS reservations, a Multi-AZ RI is worth twice as much as a Single-AZ RI.  This applies for both in NFUs (Normalization Factor Units) and in cost which may lead to the Optimizer appearing to over-recommend Single-AZ RIs if you look at RI count.  Since Single-AZ RI's are worth half as much, it's recommended that you review the nature of the RI's (single or multi-AZ) in the quote if you believe there is an issue.  The Optimizer algorithm is designed to get the most savings without over-provisioning RI purchases. 

For information on Multi-AZ reservations, see AWS documentation here:  https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.MultiAZ.html