Hi @William Tomsha ,
Welcome to the Q&A Forum!
According to your requirement description, you want to have a dynamic retrospective report on the storage of each site. Unfortunately, as far as I know, SharePoint does not have out-of-the-box monitoring dashboards or other ways to count the data you need, so I think you need to spend energy on finding the right three-party tool dashboard.
In addition, what we can do is to use PowerShell to export csv files to create storage analysis reports for the site, but it needs to be manually executed and recorded on a regular basis, and the previous site storage situation cannot be viewed.
Since I don't know the SharePoint version you are using, take SharePoint Online as an example, you can refer to this article: Get Site Collection Storage Size – Quota Usage Report using PowerShell.
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