Overview of Active Directory Components

           Active Directory information is divided into four partitions: domain, configuration, schema, and application. These directory partitions are the replication units in AD DS.

Domain Partition: Contains all objects in the domain’s directory. Domain objects replicate to every domain controller in the domain, and include user and computer accounts and groups.

Configuration Partition: Contains configuration information for AD DS and applications, including Active Directory site and site link information. In addition, some distributed applications and services store information in the configuration partition. This information replicates through the entire forest, so that each domain controller retains a replica of the configuration partition.

Schema Partition: Known as the Schema Master, is the first domain controller installed in an Active Directory forest.Contains definition information for all object types and their attributes that you can create in AD DS. This data is common to all domains in the forest, and AD DS replicates it to all domain controllers in the forest. However, only one domain controller maintains a writable copy of the schema.

Application Partitions: Can be create application partitions manually, and an application can automatically create partitions during its installation process. Application partitions hold specific application data that the application requires. The main benefit of application partitions is replication flexibility. We can specify the domain controllers that hold a replica of an application partition, and these domain controllers can include a subset of domain controllers throughout the forest. Exchange Server 2013 does not use application partitions to store information.