Does a SQL Server cluster support load balancing?

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Question

I was told by a friend, that at his last company they had a SQL Server environment which contained four clustered servers that were load balanced. So in effect, when they pulled the plug on one server, the other three would adjust and pick up the load.

From my experience of setting up and using Windows and SQL Server clustering, I cannot for the life of me understand how this is possible. Could you please correct my thinking here and let me know if this is possible using native Microsoft clustering, or load balancing, or both?

Answer

You are correct, and your friend is confused. Windows clustering, nor SQL Server clustering, does not natively support load balancing. Clustering's sole purpose is for boosting fault tolerance. When a cluster fails over, all that happens is that the instance of SQL Server running on the failed server is moved to another server. If the server that is being failed over to already has an instance of SQL Server running on it, it will now have two instances, and performance mostly likely will suffer.

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