Microsoft has included a Domain Name System (DNS) Server service in versions of Windows Server since Windows NT 4.0. DNS is a hierarchical, distributed database that contains mappings of DNS domain names to various types of data, such as IP addresses. With Windows Server 2008, the DNS Server service includes new
background zone loading, enhancements to support IPv6, support for read-only domain controllers (RODCs), and the ability to host global single-label names.
Background Zone Loading: The DNS Server service in Windows Server® 2008 makes data retrieval faster by implementing background zone loading. In the past, enterprises with zones containing large numbers of records in Active Directory® experienced delays of up to an hour or more when the DNS Server service in Windows Server 2003 tried to retrieve the DNS data from Active Directory on restart. During these delays, the DNS server was unavailable to service DNS client requests for any of its hosted zones.
To address this issue, the DNS Server service in Windows Server 2008 retrieves zone data from Active Directory in the background after it starts so that it can respond to requests for data from other zones. When the service starts, it creates one or more threads of execution to load the zones that are stored in Active Directory. Because there are separate threads for loading the Active Directory-based zones, the DNS Server service can respond to queries while zone loading is in progress. If a DNS client requests data in a zone that has already been loaded, the DNS server responds appropriately. If the request is for data in a zone that has not yet been entirely retrieved, the DNS server retrieves the specific data from Active Directory instead.
This ability to retrieve specific data from Active Directory during zone loading provides an additional advantage over storing zone information in files—namely that the DNS Server service has the ability to respond to requests immediately. When the zone is stored in files, the service must sequentially read through the file until the data is found.
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