Directory Server stores data in high-performance, disk-based LDBM databases. Each database consists of a set of files that contains all of the data that is assigned to this set. You can store different portions of your directory tree in different databases. Imagine, for example, that your directory tree contains three subsuffixes, as shown in the following figure.
The data of the three subsuffixes can be stored in three separate databases as shown in the following figure.
When you divide your directory tree among databases, the databases can be distributed across multiple servers. This strategy generally equates to several physical machines, which improves performance. The three databases in the preceding illustration can be stored on two servers as shown in the following figure.
When databases are distributed across multiple servers, the amount of work that each server needs to do is reduced. Thus, the directory can be made to scale to a much larger number of entries than would be possible with a single server. Because Directory Server supports dynamic addition of databases, you can add new databases as required, without making the entire directory unavailable.