Why are there discrepancies between the platform and AWS on S3 actual size and Object count under Usage report?

Products

• CloudHealth

Issue/Introduction

S3  actual size and Object count that appears on usage reports are sourced from the CloudWatch classic collection and not from the bill.  It is collected via CloudWatch collection.

If the object version is enabled on S3,  CloudWatch metrics will show the count of all versions of the objects in the bucket, including the latest version and any previous versions.  This means that the object count metric will reflect the total number of object versions in the bucket, not just the number of unique object keys.

CloudWatch will also include the total size of all versions of the object in the reported size metric if object versioning is enabled in S3.  This is because enabling versioning in S3 creates multiple versions of the same object, each with a unique version ID and a separate size.  CloudWatch will aggregate the sizes of all versions of the object and report the total size as the metric value.
 
So, if there is a mismatch in Object count/Size between the platform and AWS, please check if Versioning is enabled on S3.