AlwaysOn is the latest addition in the list of high availability features hosted by SQL Server. Introduced in the year 2012, AlwaysOn enables the users to create several copies of a highly available database by making use of WSFC or Windows Server Failover Custer. At times, users require implementing Availability Group on a Failover Cluster Instance. It is to be noted that for doing this, the user does not require to create separate Windows Server Failover Clusters to do so. Moreover, all the nodes for the availability group must be present on a single WSFC and that too within the same Active Directory Domain. In this write-up, we are Adding AlwaysOn Availability Group to Existing Failover Cluster.
How to Setup Availability Group to an Existing Failover Cluster?
In this section, we are going to learn the process with which the users can setup AlwaysOn availability group via two methodologies. The method deals with the process to combine existing Failover Cluster Instance with a standalone or a failover cluster present in the secondary data center.
When Failover Cluster Is In Primary Date Center & Availability Group on a Failover Cluster in Secondary Data Center
In this scenario, the Failover Cluster Instance (FCI) is located in the primary data center and the availability group is on other FCI. As we can see from the illustration, in the Primary Database CLP_1 & CLP_2 are its nodes. Similarly, in the secondary database, the nodes are represented as CLS_1 and CLS_2.
Follow the below-mentioned procedure for adding the Availability Group:
- Add two nodes named CLS_1 & CLS_2 from the secondary data center to the existing WSFC.
- For both the nodes, configure shared storage.
- Install FCI instance using New SQL Server Failover Cluster Installation.
- Join the secondary node to SQL Server FCI ‘by using Add node .
- On newly installed FCI, enable AlwaysOn availability group.
- Define the SQL FCI owners.
When The FCI Is In Primary Data Center & Availability Group Is on a Standalone SQL Instance
As we can see from the illustration, in the Primary Database named as SQL_PV is the FCI instance and the CL_1 & CL_2 are its nodes. These nodes have been joined to the WSFC. We have to setup the standalone SA_1 instance in the AG_1 group.
Follow the below-mentioned steps to add the standalone instance:
Select SQL Server Services option and then click on SQL Server option.
Select Properties option.
Note: Since, we are adding the SA_1 node to the already present WSFC, we need to have our secondary server or the replica in the same active directory.
Now, everything is ready for setting up the AG_1 availability group amidst the two data centers.
With the help of the two procedures mentioned in the write-up, we believe that the users will be able to add AlwaysOn availability group to an existing failover cluster successfully.