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I've got a 2-node SQL Server cluster (SQL 2008 sp1) running on Windows Server 2008 R2. It's an active/passive cluster and currently, node1 is the active node.

There is an app running on node1.

I've got a requirement to put another app on the cluster. however, due to resource usage, i've been asked if node2 can be the active node for this new app.

Is this possible?? If so, do I just create a new SQL cluster, using node2 as the active app as normal??

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  • Keep in mind this will require additional licensing. In an active/passive you only need to license 1 SQL Server. In active/active you'll need to have both of them licensed. – Sean Howat Oct 28 '10 at 14:30
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Should be that simple. You'd then have an active/active cluster.

Of course, you need to consider what happens on failover: will both apps fight for memory for example?

eg you have 6GB memory but the 2 SQL Server instances are set to use 4GB = problem.

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  • Jinx! You owe me a soda. – mfinni Oct 28 '10 at 13:27
  • Thanks everyone for your answers. I've already warned the business about the memory contention issues on failover :-) – Ric Jones Oct 29 '10 at 9:08
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As others have said, it is possible but it has some performance implications, should a failover happen.

There is also another costraint: you can't have two default instances, at least one of them needs to be a named one; this is because both instances could eventually end up on the same server, and instance names would then be required to identify them.

So you'll not only need two IP addresses and two network names for your clustered instances, but you'll also have to use a named instance for at least one of them. If you are going to have SQLCLUSTER1 and SQLCLUSTER2 on your network, you will also need to either use SQLCLUSTER1 and SQLCLUSTER2\NamedInstance, or (better, in my opinion) SQLCLUSTER1\NamedInstance1 and SQLCLUSTER2\NamedInstance2. This will of course need to be referenced in your connection strings.

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  • Great point, Massimo. – mfinni Oct 28 '10 at 15:02
  • Thanks everyone for your answers. I've already warned the business about the memory contention issues on failover :-) – Ric Jones Oct 29 '10 at 9:09
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Sure, that's called Active/Active. A single instance can't be active on both nodes, so the second node has to have a second instance. Of course, if one goes down, you're now running both instances on a single node. If the business is happy running both of these apps in a resource-constrained state in the event of a single-node outage, then go for it.

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  • Thanks everyone for your answers. I've already warned the business about the memory contention issues on failover :-) – Ric Jones Oct 29 '10 at 9:10

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