How to create always on availability groups with multi-subnet failover cluster?

How to create always on availability groups with multi-subnet failover cluster?

So you decided to create Always On Availability Groups with Multi-Subnet Failover Cluster which gives you the opportunity to failover across different data centers that you have in different regions or continents. Lately, we created this scenario for our monitoring tool with 2 different Subnets.

How to add subnets to SQL Server AlwaysOn availability group?

Because not all of the IP addresses returned by DNS will be online. Now click on the “Add…” button to assign IP addresses to listener “DBlistener”. We can see all three IPs from each subnet which are added for listener “DBlistener” in the below screenshot.

How to deploy SQL Server always on availability groups?

Deploying SQL Server AlwaysOn Availability Groups requires a Windows Server Failover Clustering (WSFC) cluster and each availability replica of a given availability group must reside on a different node of the same WSFC cluster. I am assuming the readers of this post have basic knowledge about AlwaysOn and its components.

Why is SQL Server not considered a multi subnet cluster?

NOTE: This configuration is not considered as a multi-subnet failover cluster configuration because the clustered nodes are on the same set of subnets. In a multi-subnet failover cluster configuration, the IP addresses are not owned by all the nodes in the failover cluster, and may not be all online during SQL Server startup.

How to setup an AG in a multi subnet cluster?

Let’s see how to setup an AG (SQL 2016) in a multi subnet cluster (Geo cluster) in a lab environment. Two Replicas sitting in my Production Data center. (Subnet 192.168.1.x) – Sync Mode Automatic Failover. Third (Far) Replica sitting in my DR Data Center.

Which is an example of a multi subnet cluster?

The following are some examples of SQL Server FCIs that use multiple subnets: SQL Server FCI SQLCLUST1 includes Node1 and Node2. Node1 is connected to Subnet1. Node2 is connected to Subnet2. SQL Server Setup sees this configuration as a multi-subnet cluster and sets the IP address resource dependency to OR.

How to reduce downtime in a multi-subnet cluster?

To solve this, you have to set RegisterAllProvidersIP to 0, then only the online subnet’s IP will be registered with DNS. You also need to set HostRecordsTTL parameter to reduce downtime. By default it is 1200 seconds, which means that every 20 minutes Local DNS Cache will be updated and application server will learn online IP.

When did multi subnet failover support come out?

Multi-subnet failover clustering support was added in Windows Server 2012 with the addition of the “OR” technology when defining cluster resource dependencies. This allowed people to allow a Cluster Name resource to be dependent upon IP Address x.x.x.x OR IP Address y.y.y.y.

Do you need multisubnetfailover for availability group?

While the MultiSubnetFailover connection option is not required, it does provide the benefit of a faster subnet failover. This is because the client driver will attempt to open up a TCP socket for each IP address in parallel associated with the availability group.