The number of corporate directories continues to expand. The need within companies to connect multiple directories, and to share data between them, is also growing. A classic example is that when someone leaves a company, thus triggering a change in the HR database, that information is shared with the network administrator. Two primary approaches to sharing directory data are now in use. One is a virtual directory that pulls live data on demand from multiple sources using LDAP. The other is to use a metadirectory, which gathers data from multiple sources, but which copies over data periodically using synchronization tools.
Virtual directories have traditionally been criticized for having slower response times, but vendors of these products, such as OctetString, contend freshness of content is more important than speed, and argue the performance they are able to offer is comparable to metadirectories anyway.
Back in June, Cameron Sturdevant of eweek, wrote an excellent piece on why virtual directories are the next big thing. More recently, the discussion recently came to a head with a posting by Mark Wilcox called “Caching Is Evil,” which was picked up by Messaging News and other sites.
Of course, it actually depends on context. Both approaches are valid. Virtual directories and metadirectories will coexist.