I have a Windows Server 2012 Failover Clustering Instance, hosting a SQL Server 2012 Enterprise Cluster, via NODE1 and NODE2.

I need to add a new read-only Replica to this cluster: NODE3, which is a Windows Server 2012 R2.

I've activated SQL Server AlwaysOn to both FCI NODE1 and Node2.

I've tried to add the new node, NODE3, to FCI cluster services, however I'm seeing this error

cluster node could not join the cluster because it failed to communicate over the network

What do I need do to add NODE3 as a read-only replica in FCI?

1 Answer 1


The terms are being confused sadly which is causing an issue. There's WCFS (Windows Clustering Foundation Services) which FCI (Failover Cluster Instance) runs on and requires shared disks. An AlwaysOn AG can also run on WCFS but it uses non shared storage and provides live read only replicas.

In other words A FCI is a shared storage architecture and you fail over from node to node. FCI doesn't in any way provide a 'read only' solution out of the box. Usually you will do mirroring+snapshot/log shipping or something else if you only have FCI. Right now what you are doing is simply adding another failover node, not an AlwaysOn AG.

This is what you are looking for (from the link). Note the multi node cluster with shared storage and the non shared storage AG: SQL FCI + AG

Right now this is what you're doing. You're simply adding a 3rd node to the shared storage cluster: pic from: http://networksandservers.blogspot.com/2011/09/failover-clustering-iv.html

This guide works well if you already have a FCI and want to add AG to it. Just look for how to install an AG. I would go through the steps for you but there's a lot of steps and you're better off going with an actual guide with screenshots and such. Do you have somewhere to test this in? Have you tried an Azure instance to test with if not? I would not recommend doing this live to prod. Here is some good documentation from Microsoft. Are you also sure that your code is AG compliant?

If you use MSDTC or cross db transactions you could create a serious problem.

Now the bigger question is are you the person who will be supporting this and is this prod? It seems like it's important because you're utilizing both FCI and AGs. I would highly suggest you research FCI and AGs in depth before deploying to prod. There are tons of resources out there. I would highly recommend not attempting to push this through on prod with the current understanding. You might set yourself up for major failure and your HA solution can bring you down.

  • Thanks But with Current understanding whats a problem in add new Read only Replica ? I think Big Question in How to add good value to answer and helping to find best choices i Follow Microsoft White Paper show how to add FCI+ AG AS Dr solution
    – A_A
    Commented Apr 24, 2016 at 13:15
  • "Building_a_HA_and_DR_Solution_using_AlwaysON_SQL_FCIs_and_AGs v1" if it's not doable pls. explain
    – A_A
    Commented Apr 24, 2016 at 13:23
  • @A_A You can absolutely use a HA and DR solution using SQL FCI's (shared storage) and AGs (Non shared storage). It's just the way you're doing it is you're only adding a 3rd node to a FCI. You want to add an AG. The link I had listed in my answer under 'this guide works well' is a good one to just setup AG. It seems you already have your FCI setup. Are you able to check Failover Cluster Manager to ensure your FCI is setup the way you want? If so, then move on to the AG portion. Again though, I stress do not try this in prod without careful understanding and testing. Commented Apr 25, 2016 at 16:14

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