SQL Server Performance Forum – Threads Archive

mulitple instances on an active/active cluster

I’m considering an active/active cluster solution where there may be a requirement to have mulitple instances on both nodes (3 instances on each). Now, I’m sure I read somewhere that this is not recommended but I cannot find any Microsoft literature (or otherwise) indicating as such. Can anyone point me to any documentation (or any reason) that points to having multiple instances on an active/active cluster is not recommended? Or, if you have any experience with multiple instances on active/active clusters, can you let me know what your experiences were? Specifically, I want to know if there is a strong, compelling, reason not to do it. Thanks,
Karl Grambow www.sqldbcontrol.com

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Not sure whether this KBAhttp://support.microsoft.com/kb/260758/en-us elivates the point, fyi. When you have multiple instances on one machine, SQL Server 2000 uses a memory-negotiation module for load balancing to equally distribute memory resources. This memory-negotiation module determines how much memory each instance gets. Two processes can’t each use all the memory, so both SQL Server instances (and all the users of both instances) would suffer from greatly increased paging. This can be avoided using memory negotiation module. And also other option is to specify max and min memory options for each instance.
I will dig out for more information and let you know if I get it. Satya SKJ
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Hi Karl, yep I’ve run 2 node active-active clusters with three instances running on it. No issues at all, just needs more physical disks since each instance should be able to fail over irrespective of any other instance Cheers
Twan

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Thanks Twan (and Satya). That’s all I needed to know.
Karl Grambow www.sqldbcontrol.com

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