A few months ago I was performing a cloud cost analysis for a project. One of the things that stood out during the analysis was the slowly increasing EC2-Other category in AWS Cost Explorer.

After looking at the Usage Type, it appeared the size for EC2 snapshots storage was increasing day after day in the account.

During the investigation it became apparent that this trend was visible across multiple accounts. Finding the root cause took a bit of investigation, so I decided to write it down in case others would run into the same problem.

The workload

The workload was an application running on Windows EC2 instances. In a central build account, a new version of the application would be installed on a predefined Windows version and baked into a new Amazon Machine Image (AMI). To do that, an EC2 Image Builder pipeline was created that ran on a daily schedule and resulted in a new AMI with a corresponding EBS volume.…