There is an Exchange 2013 server with the mailbox and CAS roles, the application itself is installed on the C: drive, and the mailbox databases on other logical drives.
If, before installing the CU, you backup only the C: volume using Windows Server Backup, then in case of an unsuccessful CU update and the need to rollback, will it be enough to restore only the C: volume from this backup? Will the serviceability of the bases remain in their current state, provided that they remain in their places?
And it is necessary to restore the entire C volume: is it entirely or is System State enough?
Or, after the server has been rolled back to the state before the CU installation, it is necessary to roll back all the databases from the backups to the state before the CU installation, even if they were not damaged?