What is a domain controller in the context of Windows servers?
closed as not a real question by John Gardeniers, Chopper3 Nov 3 '10 at 8:43
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A Domain Controller in Microsoft networks is the central server for Active Directory. It is the server that maintains the authentication database for the entire domain. In addition to this critical role it also does:
A key thing to keep in mind is that the database the Domain Controller keeps is a distributed database. Domain Controllers in the same domain all have a copy of the same database, which means they need to be able to replicate changes to each other. Additionally, the database is a multi-master database, which means that changes to the database may be applied to any copy.
With Server 2008 there is a new type of Domain Controller, the Read-Only Domain Controller. This Domain Controller has the entire database except for the authentication parts; a selected group of users may house their authentication details on a R/O DC. The reason for this is to better serve remote offices in the case of a WAN link failure and to minimize information exposure should the R/O Domain Controller get stolen.
That's the 1000m view.