With SQL 2012, Microsoft has introduced a new high availability functionality called Always On.
This feature allows you to manage high availability for specific set of database called Availability Database.
For those who are familiar with Exchange 2010, this can be compared with DAG feature.
Prerequisites installation
To use Always On SQL feature you must deploy an Enterprise Edition of Windows Server as this is the one which includes cluster technology. Indeed, you still need cluster configuration to use Always On feature.
SQL Server 2012 Installation
First you have to install SQL 2012 to allow cluster services to use and configure SQL cluster services.
As installation option, you must select New SQL stand-alone option (not the clustered one)
Once setup program has passed all first steps, choose at the Server Role installation step SQL Features Installation to select the features to be installed
I’ll not detailed all next steps are this is a ‘classical’ SQL installation
Select the features you want to install (at least Database Engine Services must be installed of course) and configure your SQL instance (name it in case of not using the default one, define directory used…)
Cluster Creation
Then you can create the cluster.
From the Server Manager, go to Features section to add Failover Clustering feature
Then, before creating the cluster, I recommend to run the validation tool to ensure all settings are correct.
Open the Failover Cluster Manager console and click on Validate a configuration
Then follow the wizard, the only thing you have to do is to enter the server names which will be part of the cluster
Then choose to run all test and let the wizard work. Results will be shown as web page.
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Once everything is correct, you can create the cluster itself by clicking on Create a Cluster.
Follow the wizard by adding all servers which will be part of the cluster
Enter the cluster name (NetBIOS name and this will automatically create a DNS record) as well as the IP address to associated with the cluster
Quorum Disk
Then create the quorum disk
From the cluster management console, right click on your cluster just created and choose More Actions\Configure Cluster Quorum Settings
Select the quorum settings you want to apply; in my case I choose Node and File Share Majority
More details about quorum settings, see http://technet.microsoft.com/en-us/library/cc731739.aspx, http://msdn.microsoft.com/en-us/library/hh270280(SQL.110).aspx and http://msdn.microsoft.com/en-us/library/ff929171(SQL.110).aspx
Configure SQL Server to support Always On feature
Launch the SQL Server Configuration Manager console and select the SQL instance from the service node to display his properties
Go to the AlwaysOn High Availability tab and enable it
Restart the SQL instance
Create Availability Group
As all prerequisites (SQL and cluster installation and configuration) are now done, we can create availability group.
From the SQL Management Studio console, connect to your SQL cluster. If the AlwyaysOn feature has been correctly enabled, the node AlwaysOn High Availability should be available
Before adding a database to a group, you must set his recovery model to Full and then perform a Full backup
Right click on it and launch the New Availability Group Wizard if you already have SQL databases defined to be part of it and follow it
Or choose New Availability Group to create an empty availability group
You will be able to associate database later after creating this empty group by right clicking on the group and choose Add Database
To add a replica, do the same but choose Add Replica