If the data is already broken up by hierarchy and all of the clients understand how to access it that way, the number of top-level branches is small and a single Directory Server instance can hold all of the information within one or more branches. Configure the Directory Proxy Server with multiple base DNs and use simple load-balancing rather than entry balancing to simplify your deployment.
If simply breaking up the data using the existing hierarchy is not an option, for example if a large number of top-level branches must be configured, then consider using entry balancing. The contents of any single branch still must fit on a given server, because only entries that are immediate subordinates of the entry-balancing base DN may be spread across multiple servers. Any entries that are further subordinates have to be placed in the same directory server instance as their parent.
If one or more branches are so large that any single Directory Server instance cannot hold all of the data, you need to use entry balancing within that branch to divide the entries among two or more sets of Directory Servers. You may also need to change the way that the data is arranged in the server so that it uses as flat a DIT as possible, which is easier to use in an entry-balancing deployment.
In an entry-balancing deployment, there can be data that is common to all external directory servers outside the balancing point. This data is referred to as the global domain. The Directory Proxy Server entry-balancing configuration will contain at least two subtree views and associated request processors, one for the global domain and one for the entry-balancing domain. In our examples, the global domain is dc=example,dc=com and the entry-balancing domain is ou=people, dc=example,dc=com. The entry-balancing base DN, ou=people,dc=example,dc=com, is also the balancing point.