You can exclude a site from backups of a SharePoint Online app. Excluding a site does not remove that site from the app, but the site is not backed up.
From the navigation pane, go to Protect > Office 365.
The Office 365 apps page appears.
In the Name column, click the app that contains the site that you want to exclude.
The app page appears.
On the Sites tab, in the row for the site that you want to exclude, click the action button , and then click Manage > Exclude from backup.
A confirmation dialog box appears.