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First time setting up a clustered environment, and have a few questions. From a windows cluster perspective what determines if it is an Active/Active cluster vs an Active/Passive cluster? Is it the configuration of the windows cluster or the services being clustered (SQL, BizTalk, etc)?

Would Active/Active be synonymous with load balanced and active/passive be synonymous with failover?

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possible duplicate of AlwaysOn SQL Server 2012 - any option for true active/active? – mfinni Jul 20 '12 at 17:16
up vote 3 down vote accepted

First of all; Windows Failover Clustering is not a load balancing feature, it's a way to implement high availability for network resources.

So, to answer your question:

Yes and no!

Any clustered service or application is always Active/Passive (online on one cluster node, offline but available to be brought online on one or more other nodes).

Let's assume a simple cluster configuration consisting of 2 nodes (ServerA and ServerB), with 2 SQL Instances (SQLClu01 and SQLClu02).

SQLClu01 has ServerA as preferred owner, SQLClu02 uses ServerB, but they're both configured for automatic failover. When both cluster nodes are up and running, you have an "Active/Active" cluster, in the sense that you have 2 cluster nodes, each with an SQL Instance online.

However, from a service perspective, you still have an Active/Passive configuration, since any SQL Instance is always online on one node, offline on another.

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Thanks!. I see that although from a cluster perspective it's Active/Active, but from a services perspective it is effectively Active/Passive. So if you were looking to actually load balance SQL Server in addition to high availability, what would your clustering architecture look like? Would that involve multiple clusters, that use some sort of hardware/software load balancer? – Jeremy Jul 20 '12 at 17:05
With MS SQL, you cannot do true active/active for writes. You can do things that make it easy to put queries on the non-active system, but you cannot (out of the box) do active-active load-balancing of your SQL instance across multiple machines. – mfinni Jul 20 '12 at 17:15
See my link above to a dupe question with a detailed answer. – mfinni Jul 20 '12 at 17:17
Since SQL Server doesn't support multimaster replication, a true load-balanced Read-Write setup cannot be achieved. Depending on your specific need, others solutions might be feasible (NLB in front of 2 transactional replication subscribers for balanced read/select-queries for example) – Mathias R. Jessen Jul 20 '12 at 17:20

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