6.2. Distributing the Directory Data

Directory Server stores data in LDBM databases. This a high-performance, disk-based database. Each database consists of a set of large files that contain all of the data assigned to it.

Different portions of the directory tree can be stored in different databases.

For example, Figure 6.1, “Storing Suffix Data in Separate Databases” shows three suffixes being stored in three separate databases.

When the directory tree is divided between a number of databases, these databases can then be distributed across multiple servers. For example, if there are three databases, DB1, DB2, and DB3, to contain the three suffixes of the directory tree, they can be stored on two servers, Server A and Server B.

Server A contains DB1 and DB2, and Server B contains DB3.

Distributing databases across multiple servers reduces the workload on each server. The directory service can therefore be scaled to a much larger number of entries than would be possible with a single server.

In addition, Directory Server supports adding databases dynamically, which means that new databases can be added when the directory service needs them without taking the entire directory service off-line.

Each database contains the data within a specific suffix of the Directory Server. Both root and subsuffixes can be created to organize the contents of the directory tree. A root suffix is the entry at the top of a tree. It can be the root of the directory tree or part of a larger tree designed for the Directory Server. A subsuffix is a branch beneath a root suffix. The data for root and subsuffixes are contained by databases.

For example, Example Corp. creates suffixes to represent the distribution of their directory data.

Example Corp. can spread their directory tree across five different databases, as in Figure 6.4, “Directory Tree Spread across Multiple Databases”.

The resulting suffixes would contain the following entries:

The dc=example,dc=com suffix is a root suffix. The ou=testing,dc=example,dc=com suffix, the ou=development,dc=example,dc=com suffix, and the ou=partners,ou=development,dc=example,dc=com suffix are all subsuffixes of the dc=example,dc=com root suffix. The root suffix dc=example,dc=com contains the data in the ou=marketing branch of the original directory tree.

The dc=example,dc=com entry represents a root suffix. The entry for each hosted customer is also a root suffix (o=example_a and o=example_b). The ou=people and the ou=groups branches are subsuffixes under each root suffix.