Dgraph replicates all data within a group. A single cluster can can many groups, each group consisting of 1,3 or 5 servers.
Tablets (predicates) only belong to one group. The cluster can serve requests across all groups, however it does this by forwarding any part of the request that deals with non-local data to a node that has that data.
You can control exactly which group serves which tablets, though this must be done externally with the moveTablet http API on the zero (this is when self hosting). This can be paired with disabling auto-rebalancing on the zeros to give you complete control over data locality.