To gauge the usage of Enterprise Vault when it runs with particular settings, you can run tasks in report mode. In this mode, Enterprise Vault does not archive items but produces a report about what would be archived on a normal run.
The reports are logged in a file in the Reports folder, which is a subfolder of the Enterprise Vault installation folder. The fields in the file are tab-separated, so you can easily import the file contents into a spreadsheet program such as Microsoft Excel.
The following are examples of the types of reports that are generated:
Exchange mailbox preparation. When processing Provisioning Groups, the Provisioning task reports on mailboxes that have been prepared for archiving and the policies assigned.
PST migration. In the case of Locate and Migrate there are separate reports for each phase of the migration: Location, Collection, and Migration.
In the Administration Console, Vault Store Usage Reporter can generate different reports detailing vault store usage.