Rebalancer Settings after Upgrading from an Earlier Release
For a brand new database, the rebalancer is enabled by default and the assignment policy is bucket. The bucket policy moves less data than the legacy policy when adding or deleting a forest and it is still deterministic.
After upgrading from an earlier release of MarkLogic Server, the rebalancer is disabled on existing databases and the policy is set to legacy.
At the forest level, in both cases, the rebalancer is enabled by default.