How to configure SQL server Fail over clustering Instance (FCI).

This blog is part of a SQL HA-DR solution series , In my previous blogs I mentioned how Log Shipping, Mirroring & AlwaysOn Availability Group can be configured, now here you will get step by step procedure for SQL Fail Over Cluster Instance (FCI) high Availability solution. SQL FCI is sometime also known as AlwaysOn FCI and it’s bit different then AlwaysOn AG (Availability group). Always ON FCI need shared storage that is accessible from all the participant node and it provide instance level high availability.  If your primary (or active) server is down then secondary (passive) take responsibilities for all SQL operation.

The details about SQL FCI can be found here.

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Unable to re-create Availability group with same name

While working in my test environment, we have delete existing Availability group and try creating a new one with same name. Unfortunately It was failing with error  “Failed to create availability group ‘SQL AAG’, because a Windows Server Failover Cluster (WSFC) group with the specified name already exists.”


We successfully deleted existing configuration as per Microsoft & Fail-over cluster log does not give any clue about existing AAG group.

Here is the solution.

  1. Drop the availability group if not in previous attempt, refer
  2. Take backup of registry then delete key “HKEY_LOCAL_MACHINE\Cluster \HadrAgNameToldMap” from all nodes participating in cluster.
  3. From SQL configuration manager, uncheck ‘Enable Alwayson Availability Groups’, apply OK. Restart SQL service.config
  4. Check the box ‘Enable Alwayson Availability Groups’ again, Apply-ok, restart SQL service.

Now you should be able to create availability group with same existing name.


#aag, #alwayson