Always On–New Feature: “Availability Group” in Denali

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In Denali, there is a new feature called – Availability Group.  

With this feature you can setup –

  • Multiple Database mirroring as part of Availability Group – This is perfect for an application that uses multiple databases
  • Multiple Secondaries
  • Example:
  • one for HA with Synchronous with Automatic Failover -- in Same datacenter
  • 2nd one for HA with Synchronous with Manual Failover with Reporting capability (without doing Snapshor DB – this is a great feature where you can direct your Reporting Workload to while giving the best to your OLTP) -- in same datacenter
  • 3rd one for DR with Asynchronous with Manual Failover – in a different data center
  • ..
  • Up to 5 secondaries can be involved as part of Availability group
  • Active Secondary – as I mentioned earlier you can have Live Reporting going off of one of the Secondary
  • Fast Client Connection Redirect using DNS aliasing

Cool thing about this is – wizard does it all, as supposed to pre and post tasks with current Database Mirroring setup where we have to take a backup of database, copy the backup over to secondary, and then restore it with NORECOVERY option. In Denali, it does it all as part of Availability Group setup wizard. 

To illustrate above scenario, I created below diagram – should explain. As you can see, Availability Group is built upon WSFC (Windows Server Failover Cluster) technology, that means, each of this servers have to be part of WSFC configuration – no need for SQL Server Failover Cluster instance, though – that’s a totally separate HA architecture. 

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