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Chapter 27: Database Mirroring
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■ (^) Each computer participating in an availability group must be part of the same
Windows Server Failover Clustering (WSFC) cluster. Availability replicas must be
hosted by different nodes of the same WSFC cluster.
■ The host server must be a Windows Server Failover Cluster node. Each instance of
SQL Server that hosts availability replicas for a given availability group must reside
on separate nodes within a single WSFC cluster.
■ (^) Each instance of SQL Server 2012 in the availability group must run Enterprise
Edition. Core editions of SQL Server are supported; however, you cannot mix modes
(that is, Windows Server Core and Windows Server full UI in the same WSFC sup-
porting an availability group).
■ (^) Each instance in an availability group must use the same SQL Server collation.
■ Databases in an availability group must be in Full recovery model.
■ (^) Only user databases may belong to an availability group.
■ If you use contained databases in an availability group, the server option for con-
tained database authentication must be set to 1 on every instance that hosts an
availability replica for the availability group.
AlwaysOn Availability Groups, while being a powerful new addition to the SQL Server 2012 feature set, can be com-
plex and confusing. A great resource to help clarify many of the questions that come up for AlwaysOn Availability
Groups is an FAQ page maintained by Clustering MVP Allan Hirt. You can fi nd his AlwaysOn Availability Groups FAQ
page at http://www.sqlha.com/2012/04/13/allans-alwayson-availability-groups-faq/.
Confi guring AlwaysOn Availability Groups
To deploy AlwaysOn Availability Groups, you must fi rst set up a Windows Server Failover
Clustering (WSFC) cluster. Each availability replica within an availability group must be on
its own node in the same WSFC cluster. Figure 27-14 shows this setup.
- Ensure all nodes participating in the cluster group have the .NET Framework 3.5.1
and the Failover Clustering features enabled. To enable these features, from the
Server Manager click the Features node. From the Features page click the Add
Features link on the right side. - When the .NET and Clustering features are enabled, you can confi gure the cluster.
To confi gure the cluster go to Control Panel ➪ Administrative Tools ➪ Failover
Cluster Manager, and click Validate a Confi guration. - In the Validate a Confi guration Wizard, provide the names of the SQL Servers that
need to be confi gured. After you provide the server names, select the Run All Tests
(Recommended) option. When the tests fi nish, the Failover Cluster Validation
Report, as shown in Figure 27-15, shows any issues with your confi guration. Click
Finish to complete validation.
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