Microsoft moved Windows 2000 to extended
support in June, pushing the elderly Windows NT operating system one step
closer to the software graveyard. While more than a few organizations are still
holding on to the OS, sooner or later, something has to give.

Many of those organizations currently running NT are
considering making the move to Windows Server 2003. But before beginning this
considerable upgrade, it’s important to understand some key differences between
Active Directory and the NT 4 domain model as it pertains to server roles.

In NT 4, there are primary domain controllers (PDCs) and
backup domain controllers (BDCs). Only one PDC can exist per domain. The PDC
hosts a read/write copy of the domain database, and the BDCs each house a
read-only version of the same information, thus providing some measure of
redundancy and infrastructure scalability.

But in the event of a loss of the PDC, you can’t make
changes to the domain until you replace it. However, users can continue to log
in using a BDC.

In Active Directory, with the exception of specific roles
(i.e., Flexible Single Master Operations, or FSMO), all domain controllers
function equally. The system replicates changes made to read/write versions of
the domain database to all other domain controllers, resulting in a much more
robust and scalable infrastructure. A single domain controller does serve the
FSMO roles, but you can move these roles to any other domain controller at will.

Another key difference between NT and Active Directory is
the process by which a server becomes a domain controller. In NT, once a server
is a PDC or a BDC, only reinstalling Windows can downgrade it to a member
server (and vice versa).

But in Windows 2000 and Windows Server 2003, you use the
DCPromo utility to handle this process. This utility can upgrade and downgrade
servers to and from domain controllers and member servers.

Of course, keep in mind that these differences are really
just the tip of the iceberg.

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