Designing a Scaled Deployment

The basic deployment described in Chapter 9, Designing a Basic Deployment assumes that a single Directory Server is enough to satisfy the read and write requirements of your organization. Organizations that have large read or write requirements, that is, several clients attempting to access directory data simultaneously, need to use a scaled deployment.

Generally, the number of searches a Directory Server instance can perform per second is directly related to the number and speed of the server's CPUs, provided there is sufficient memory to cache all data. Horizontal read scalability can be achieved by spreading the load across more than one server. This usually means providing additional copies of the data so that clients can read the data from more than one source.

Write operations do not scale horizontally because a write operation to a master server results in a write operation to every replica. The only way to scale write operations horizontally is to split the directory data among multiple databases and place those databases on different servers.

This chapter describes the different ways of scaling a Directory Server Enterprise Edition deployment to handle more reads and writes. The chapter covers the following topics:

• Using Load Balancing for Read Scalability

• Using Distribution for Write Scalability

• Using Referrals For Distribution