* Learn more about the two forms of cache: in-memory and persistent
In critical operations such as identification, authentication and authorization, a virtual directory needs to provide guaranteed fast access to information. In many cases, the virtual directory needs to read faster than underlying sources can deliver. It can accomplish this through caching mechanisms.
Cache is king for virtual directories
By Michel Prompt
Virtual directories are touted for their flexibility, but the technology isn’t known for its speed. A virtual directory adds an extra layer of software and intermediate TCP/IP hop. Factor in the dynamic transformation, the join of data from disparate directories and the reorganization of the underlying namespaces, and a virtual directory will always be slower than the sources it virtualized.
But in critical operations such as identification, authentication and authorization, a virtual directory needs to provide guaranteed fast access to information. In many cases, the virtual directory needs to read faster than underlying sources can deliver. It can accomplish this through caching mechanisms.
A virtual directory can be divided into two layers. The front end handles the Lightweight Directory Access Protocol (LDAP) or another standard protocol, and the back end maps and transforms the data from the virtualized sources (directories, databases and/or applications). The back end represents the virtualization layer, and the virtual directory’s performance depends on the scalability and speed of the back end.
A virtual directory needs access to the underlying virtualized data sources. Without a caching strategy, a virtual directory acts as a proxy, forwarding the calls to the underlying sources. Even with the best optimization at the front-end level, a virtual directory will deliver only a fraction of the speed of underlying sources.
There are essentially two forms of cache: in-memory and persistent. To read about them, go to: http://www.networkworld.com/news/tech/2005/101705techupdate.html?rl
