In layman terms, what does it mean to have "Active/Active"? What are the steps to achieve this configuration?

Edit: We currently have an "Active/Passive" setup which isn't efficiently making use of the hardware so we need a "Active/Active" configuration.


Active/Active could mean two things (or maybe others depending on the project manager's imagination).

  1. At least two clustered instances of SQL Server on two nodes of a Windows cluster. This allows both pieces of hardware to be used simultaneously and not wasted, one server for each instance, with the worst case scenario being one server fails and the other takes all of the load for both instances in that case.

  2. More likely, a manager thinks that both nodes of a cluster could be actively running the same instance of SQL Server, with reads and writes going to both. This is not how clustering works; it is not for scale out but for high availability / disaster recovery. But it is a common misconception, especially for managers. :-)

Most people that work with clustering regularly cringe when they hear active / active. It's inaccurate, ambiguous, and to them it's like nails on a chalkboard.

  • Thx Aaron. What are the various (read: easiest to the toughest :) ) ways by which we can achieve this? – prasanth Jul 12 '12 at 16:34
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    To achieve what? You need to determine what exactly your manager expects you to achieve before anyone can tell you how to achieve it. Do you have multiple instances of SQL Server on your cluster? – Aaron Bertrand Jul 12 '12 at 16:35
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    What does "Active/Active" mean to you? What does "one instance (which is passive)" mean? – Aaron Bertrand Jul 12 '12 at 17:58
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    @swasheck I think it's about wasted hardware. I think the manager thinks that "converting" the cluster to active/active will allow a single instance to utilize both servers simultaneously (which really is a common misconception I encounter a lot). And I think the concepts here like "Active" and "Passive" are grossly misunderstood. I shouldn't have to say "think" so many times in a comment... – Aaron Bertrand Jul 12 '12 at 18:17
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    as @AaronBertrand noted, active/active does not mean that one instance can leverage double hardware. if you're trying to shed load on the "active" node (the one with the extant sql server instance) by putting another sql instance on the other node, it's going to have a different name. you will then need to migrate the databases on the extant instance to the new instance. then you'll need to refactor your code such that it connects to this new instance. – swasheck Jul 12 '12 at 18:33

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