Hi Emil,
The Archive size report in Archive Manager allows you to get an overview of the size of mailboxes in the HSM store. For additional information, please refer to the following:
How to calculate size of user mailbox?
metalogix.force.com/.../How-to-calculate-size-of-user-mailbox
Archive size report
www.metalogix.com/.../Archive_Manager_Exchange_Edition_-_Admin_Manual.pdf
On the other hand, ControlPoint allows you to archive audit log data. To know more about it, please refer to the article below, which includes a video that discusses how to set up and use the archive audit data feature of ControlPoint:
QUICK TAKES: Setting Up and Using the Archive Audit Data Feature
metalogix.force.com/.../QUICK-TAKES-Setting-Up-and-Using-the-Archive-Audit-Data-Feature
I hope this helps.
Regards,
Cyrus