Directory Server 8.1 is comprised of several components, which work in tandem:
• The Directory Server is the core LDAP server daemon. It is compliant with LDAP v3 standards. This component includes command-line server management and administration programs and scripts for common operations like export and backing up databases.
• The Directory Server Console is the user interface that simplifies managing users, groups, and other LDAP data for your enterprise. The Console is used for all aspects of server management, including making backups; configuring security, replication, and databases; adding entries; and monitoring
servers and viewing statistics.
• The Administration Server is the management agent which administers Directory Servers. It communicates with the Directory Server Console and performs operations on the Directory Server instances. It also provides a simple HTML interface and on-line help pages. There must be one Administration Server running on each machine which has a Directory Server instance running on it.
Example video from Youtube demonstrates the basic installation of the cluster.