When you add a second Microsoft Windows 2000 domain controller, Active Directory
becomes a distributed database. Installing Active Directory automatically
upgrades a member server to become a domain controller. There is no primary AD
domain controller.
Active Directory services, along with the AD database, authenticate domain
users, administer installation policies and manage desktop practices and
software. The directory package also comes with management tools.
Depending on the type of change you're making to Active Directory, each
management role or process resides on one server in each domain. So when a
systems administrator makes a change to the Active Directory schema, only one
domain controller in the enterprise can make that change to the database.
Similarly, when a new domain is created, only one domain controller can add the
domain to the database. When there's just one domain controller, all
management roles and the Active Directory global catalog reside on that server.
As you create more controllers and the database becomes distributed, the roles
and the global catalog can be dispersed among them.
Once the Active Directory database resides on more than one domain controller,
it's a good idea to frequently record which server is performing what
AD-operations role. AD comes with utilities that document which domain
controller plays what role, but it's easier to use the AD management console
(MMC) snap-in because it's graphical user interface-based.
Active Directory's backup is usually performed with the backup wizard. Beware,
however, that when you mark the System State checkbox, the backup utility only
archives the AD database, the AD checkpoint file and the AD logs for a single
controller. You have to back up each controller individually with the wizard.
Not all controllers need their database archived, however, so take a close look
at how AD uses each domain controller.
With the AD distributed database, replication is the key to ensuring that
changes to one controller's copy of the database is sent to all domain
controllers. A single domain controller does not notify each controller -
it's a round-robin process. Replication helps the recovery of an updated database under
typical emergency conditions (unlike Gulf Coast Community College's
situation), such as when a single domain controller is lost or when that controller's AD
database becomes corrupted.
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