AD Replication
There are four Active Directory partitions on each domain controller:
- Domain. This contains all the objects stored in a domain, including users, groups, computers, and Group Policy containers.
- Configuration. This contains objects that represent the logical structure of the forest (including information about domains), in addition to the physical topology, including sites, subnets, and services.
- Schema. This defines the object classes and their attributes for the entire directory.
- Application. Domain controllers also can host application partitions. You can use application partitions to limit replication of application-specific data to a subset of domain controllers.
Each domain controller maintains a copy (or replica), of several partitions:
- The configuration partition and schema partitions replicate to every domain controller in the forest.
- The domain partition for a domain replicates to all domain controllers within a domain, but not to domain controllers in other domains.
Therefore, each domain controller has at least three replicas: the domain partitions for its domain, configuration, and schema.