Question: I want to efficiently manage my data storage, which I can view by going Components -> Disk Usage. But, I'm not certain what data is counting against my storage limit. Is it counting things I've uploaded to the Media Manager? What about data in Events, or other Salesforce components?
Answer: Only files that have been uploaded to your storage directory count against your data limit. If you have uploaded items via the Media Manager, or the WYSIWYG editor in an article or module, for example.
Data for events does not count against your storage limit, however, images that you upload to display on an event, or a PDF file that you've uploaded for attendees to download, would.
If you want a clear view of everything that is counting against your storage limit, look at the Media Manager at Site -> Media Manager.