Performing a Site SurveyChapter 2 How to Plan Your Directory Data 35Considering a Data MasterThe data master is the server that is the master source of data. Consider whichserver will be the data master when your data resides in more than one physicalsite. For example, when you use replication or use applications that cannotcommunicate over LDAP, data may be spread over more than one site. If a piece ofdata is present in more than one location, you need to decide which server has themaster copy and which server receives updates from this master copy.Data Mastering for ReplicationDirectory Server allows you to contain master sources of information on more thanone server. If you use replication, decide which server is the master source of apiece of data. Directory Server supports multi-master configurations, in whichmore than one server is the master source for the same piece of data. For moreinformation about replication and multi-master replication, see chapter 6,“Designing the Replication Process,” on page 111.In the simplest case, put a master source of all of your data on two DirectoryServers, and then replicate that data to one or more consumer servers. Having twosupplier servers provides safe failover in the event that a server goes off-line. Inmore complex cases, you may want to store the data in multiple databases, so thatthe entries are mastered by a server close to the applications which will update orsearch that data.Data Mastering for SynchronizationYou can synchronize your Directory Server users, groups, attributes, andpasswords with Microsoft Active Directory or Windows NT4 Server users, groups,attributes, and passwords. If you have two directory services, you must decide ifyou want these to be synchronized (if they will handle the same information), whatamount of that information will be shared, and which service will be the datamaster for that information. The best course is to choose a single application tomaster the data and allow the synchronization process to add, update, or delete theentries on the other service. For more information, see chapter 7, “DesigningSynchronization,” on page 139.Data Mastering Across Multiple ApplicationsYou also need to consider the master source of your data if you have applicationsthat communicate indirectly with the directory. Keep the processes for changingdata, and the places from which you can change data, as simple as possible. Onceyou decide on a single site to master a piece of data, use the same site to master allof the other data contained there. A single site simplifies troubleshooting if yourdatabases get out of sync across your enterprise.
