You have configured a multirack Database Machine with two X9M-8 full racks all in a...

In order to monitor all components of this multirack configuration, Enterprise Manager agents must be deployed on at least two storage servers in both racks and all database servers in both racks. This is according to the Oracle Exadata Database Machine X9M Implementation Essentials official text book [1], in which it states "To monitor all components of the multirack configuration, you must deploy agents on all database servers and at least two storage servers in each rack" (page 6-15).