Using Alfresco Explorer's Administrative console, you can track the users' usage within the DM repository, as shown in the following screenshot:
You can also set quotas for a given user. The usage is based on the content size (in bytes) and is typically displayed in KB (kilobytes), MB(megabytes), or GB(gigabytes).
When a user adds or edits content beyond his or her quota, an error message will be displayed, stating that the user has exceeded his or her quota.
Individual users can check their quota and usage, by using Alfresco Explorer's User Profile settings page.