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Kenny
Asked: 2012-08-04 05:50:29 +0800 CST

SQL Server 2012 Mirroring / AlwaysOn - need for SAN?

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There appears to be a great deal of conflicting information about whether or not SAN is required for a Sql Server 2012 Mirroring setup.

I currently have an Active-Passive-Witness SQL 2008R2 setup where each of the machines in the setup have plain old DAS raid arrays.

I would like to implement exactly the same again with SQL Server 2012, however much of the online documentation (e.g. Prerequisites, Restrictions, and Recommendations for AlwaysOn Availability Groups (SQL Server) - http://msdn.microsoft.com/en-us/library/ff878487.aspx) suggests each node in the "AlwaysOn Availability Group" must be a node of a Windows Server Failover Clustering (WSFC) cluster.

I'm not trying to set up a SQL Server Failover Cluster - only database mirroring between two instances of SQL Server (active-passive-witness).

When I look up the requirements for setting up a Windows Server Failover Clustering (WSFC) cluster I always see SAN / shared storage as a requirement.

However I have seen a pretty definitive answer to my question here: "AlwaysOn Availability Groups do not require deployment of a Failover Cluster Instance or use of symmetric shared storage (SAN or SMB)." - http://msdn.microsoft.com/en-us/library/hh270278.aspx - but am unsure what to believe.

Has anybody out there tried an Active-Passive-Witness mirroring setup with SQL Server 2012 and "AlwaysOn Availability Groups" where you didn't need to use SAN / shared storage?

Many thanks,

Kenny

high-availability

1 Answers

  1. Database mirroring (DBM) and availability groups (AG) are two different features. DBM is deprecated in SQL Server 2012 and availability groups are new. AGs can be configured on standalone instances that are insalled on WSFC (Windows Server Failover Clustering) nodes. There is no witness with AGs, and even with DBM, a witness was only required in high safety mode with

    There are quite a few people who have deployed AGs.You shouldn't be using DBM at this point, and you should never use DBM + FCI (Failover Cluster Instance) in high safety.

    Also, please stop using active/passive. It's wrong for FCI, and definitely not even remotely applicable for AGs or DBM. http://www.sqlha.com/2012/01/09/once-more-with-feeling-stop-using-activepassive-and-activeactive

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