Before delving into the details of how hardware affects directory server performance, it is helpful to understand what performance capabilities are needed in terms of directory server software.
As your e-business infrastructure becomes more complex and mission critical, the directory services must scale vertically and horizontally to meet your needs of today and the future.
Vertical scalability is achieved by adding additional RAM and disks to an existing machine to improve performance and to minimize data center sprawl. The scalability of the directory server can also be observed as you add additional CPUs. Although the server performance does improve with each additional CPU (up to about 12), adding the thirteenth CPU yields a much smaller improvement than adding the second or third. Directory services software must be designed to take advantage of vertical scalability. It should also be noted that the above information about the number of CPUs is for the Sun ONE Directory Server 5.2 software. Other versions of the directory server will likely have different levels of scalability. For instance, we know this is true for version 5.1, which only scales to about 8 CPUs.
Horizontal scalability of reads and writes through the directory server can be achieved through adding more replicas, but the ability to have more master servers does not significantly improve write performance because all the changes must still be applied on all masters.
The Sun ONE Directory Server software provides these vertical and horizontal scalability requirements. Some of the key performance features of the Sun ONE Directory Server 5.2 software are: