https://docs.oracle.com/en/engineered-systems/exadata-database-machine/dbmmn/maintaining-exadata-storage-servers.html#GUID-AE16A1DA-53C6-4E80-94E5-963AA65373AB The two commands that must be executed to safely power off the storage server in an Exadata X9M Database Machine are E and F.
Command E, CellCLI alter GRIDDISK all inactive, will deactivate all of the GRIDDISKS on the affected storage server. This will ensure that no data is lost during the power-off process.
Command F, shutdown -h now, will shut down the storage server. This will ensure that the storage server is completely powered off and no data is lost.
For more information on how to properly power off an Exadata Storage Server, refer to the Oracle Exadata Database Machine X9M Implementation Essentials official text book and resources [1][2].