Rolling Upgrades
Encryption at rest is a feature introduced in MarkLogic Server 9. Clusters running older versions need to be completely upgraded to MarkLogic Server 9 before using this feature. See Rolling Upgrades in Administrating MarkLogic Server for more about rolling upgrades.
Note
During upgrades, the default passphrase for the upgraded system is not set. You will need to reset the default passphrase after an upgrade.