I am always deep lover of Directory Server and technology behind it. I was very happy when I saw that Sun (I have worked mostly with Sun LDAP and I love it) is aggressively working on a open source directory server project OpenDS which will take the directory server to new levels. I was reading about the intension of this project and why they have not supported the current open source projects like openLDAP,Apache directory etc and the reason they feel is because they want to redesign it based on current client's requirements.
Below are the features in the openDS:
Performance Lots of features are important, but performance is almost always near the top of the list. It needs to be extremely fast, outperforming all other servers wherever possible.
Upward Vertical Scalability. It needs to be capable of handling billions of entries in a single instance on appropriately-sized hardware. It should be able to make effective use of multi-CPU, multi-core machines with hundreds of gigabytes of memory.
Downward Vertical Scalability. It needs to be capable of running adequately in low-memory environments so that all essential components can be functional on edge devices like cell phones and PDAs.
Horizontal Scalability. It needs be possible to use synchronization to achieve higher levels of read scalability by adding servers to the directory service. In addition, it needs to be possible to use data distribution in conjunction with synchronization to achieve horizontal read and write scalability to achieve deployments into the billions.
Supportability. The server should be easy to support and maintain. Administration should be intuitive, and wherever possible the server should provide sufficient information and notifications to enable corrective actions, even predictively.
Security. The server must provide extensive security in areas like access control, encryption, authentication, auditing, and password and account management.
Extensibility. Virtually every aspect of the server should be customizable. It needs a safe and simple plugin API that delivers additional points of extensibility, including, but not limited to, password validation algorithms, password generators, monitor information providers, logging subsystems, backend repositories, protocol handlers, administrative tasks, SASL mechanisms, extended operations, attribute syntaxes, and matching rules.
Synchronization. The server must support data synchronization between instances, including not only total data synchronization but also partial synchronization (with fractional, filtered, and subtree capabilities), and must also provide a means of synchronizing with other applications and data repositories.
Availability. The server must be robust enough to continue running properly even if serious errors are encountered.
Portability. The server needs to be written entirely in Java so that it can run on any platform.
Reliability. A directory service is one of the most critical components of a business infrastructure. It is absolutely essential that the service function despite hostile or unexpected events and that the data it delivers be trusted.
Compatibility. The Sun Java System Directory Server will continue to be maintained over time and will not be immediately replaced by Sun products based on OpenDS. However, OpenDS must provide support for virtually all existing features of the Sun Java System Directory Server. Migration from other directory server implementations should also be taken into consideration when applicable.