Quick Note on Always On Availability Groups Performance in SQL Server 2012

It’s still early in the lifecycle of SQL Server 2012 (heck, we just RTM’d 2 weeks ago and not yet GA!) but some of the whitepapers, best practices, guidance, etc. are starting to flow out and I’ll make it a point of mine to try and highlight some of these as they come out. That is, the ones that effect projects or customers that I’m working on, anyway.

So here is one that caught my eye: I saw this on Books on Line about making AlwaysOn Availability Groups perform better in terms of resolving network names and IP addresses with the AG Listener:

Always specify MultiSubnetFailover=True when connecting to a SQL Server 2012 availability group listener or SQL Server 2012 Failover Cluster Instance. MultiSubnetFailover enables faster failover for all Availability Groups and failover cluster instance in SQL Server 2012 and will significantly reduce failover time for single and multi-subnet AlwaysOn topologies. During a multi-subnet failover, the client will attempt connections in parallel. During a subnet failover, SQL Server Native Client will aggressively retry the TCP connection.

I copied that directly from the BOL link above. The bolded areas in that passage are mine and I wanted to point out that it states that adding “MultiSubnetFailover=True” is the recommendation for clients connecting to AG Listeners even in single-subnet AlwaysOn topologies (FCI’s as well). If you scroll down in that full passage, you will also note the bit about OLEDB not supporting the “MultiSubnetFailover keyword”, which gives me the opportunity to again remind everyone that OLEDB for SQL Server client connectivity has been deprecated as of SQL Server 2012.

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3 responses to “Quick Note on Always On Availability Groups Performance in SQL Server 2012

  1. Pingback: Link Resource # 43 : Mar 01 – Mar 24 « Dactylonomy of Web Resource

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