In the Admin Control Panel, select Archiving > Usage.
In the Usage page, your domains are listed, showing the status of the Archive product:
- Available - The Archive is available for this account
- Enabled - The Archive is activated for the domain, however this does not imply that there has been any activity. See Enable Archiving on a Domain
- Active - If active, the domain is actively using the Archive product
In the Storage used column, you can see how much storage is being used by the Archive for each domain. Click on the refresh icon 
to see the up-to-date storage used.