Accurately reporting the amount of data migrating out of Google Vault is key to assessing licensing needs. Google does not provide an “at-a-glance" mechanism for this, but the directions below will help you estimate Vault size.
Log in to Google Vault and create a new matter.
Within the matter, run a search that represents the planned export. Typically, the only data migrated out of Google Vault is in the hidden "Permanently Deleted" label. This label cannot be accessed separately, and is included when searching for Deleted Items. This means all deleted items within Vault will be searched.
Run a search for all users (by keeping the Accounts field blank) with this search term: in:trash (all items with "deleted" and "permanently deleted" labels). Be sure to select the checkbox labeled Exclude drafts.
Once the results are returned, click the Export results button.
Export times vary from minutes to hours depending on the size of the data set. Note that if the export takes more than 24 hours to complete, Vault will cancel or stall the export. In these cases, you will need to split the data into multiple export operations. Skip to the section below titled "What if the Export is Canceled?"
Click on Export to view progress:
Once complete, export size and item count can be viewed in the same location:
What if the Export is Canceled?
Exports can be canceled if they hit an unpublished maximum size, or take more than 24 hours to complete. In these cases, separate the exports by groups of user accounts. To do this, first gather a list of users by logging in to the G Suite Admin Console, and then selecting Users:
On the top right portion of the screen, select the triple dots and click Download users:
The result is a CSV file containing a list of users. From here, follow the sizing instructions above, but when searching, split the user list across searches:
Depending on the size of these exports, you may need to break the user lists down even further.