Let's say I have created 10 spaces. Is it possible to see how much storage is used by one specific space, if I for instance wanted to reduce the amount of storage I am using?
If you are an Admin, you can go to the gear icon "Confluence Administration" and then expand the Data Management link on the left side. There is a new report that can be downloaded called "Space Reports". It gives content and attachment counts as well as storage used in MB.