Database Mirroring for Local HA and Log Shipping for DR – Today and Tomorrow

With the release of SQL Server 2012,we have a chance to review our existing HA + DR solution and there is always an option to test and understand how this can be replaced/enhanced in SQL 2012.

Lets look at the below example (This is just one example,we have multiple HA,DR solutions) of one of the famous and most used HA + DR situation before the release of 2012 –

Database mirroring has been really flexible and this feature has been used as a HA solution for the primary data center.In the event of a failure the mirrored database will be live and users will be connected to it.The primary data center involves a witness server too,which will facilitate automatic failover.

The DR site has been configured with a lop shipping secondary and in the event of primary DC failure,this database will be used for connections.This cannot be automated and there is always a manual intervention.

There is potentially no data loss for database mirroring situation within the primary DC,however log shipping involves data loss.

After SQL Server  2012

We have DBM still in 2012,however this feature is deprecated.This simply means that future versions of SQL Server wont come with DBM facility and we need to use Always ON Availability Groups instead.

With 2012 we will be creating Windows Server Failover cluster between primary site and DR site and we will add all the nodes to this cluster.The next part will be creating availability groups for the required set of databases.In the above example we will have synchronous data transfer for the secondary replica within the primary DC.We can have either syn or async transfer for the secondary replica at the DR site.

The beauty of this solution is we can have readable secondaries.We can have up to 4 secondaries.

With Availability Groups we have the flexibility of grouping databases which needs to be failed over during an event.We can have automatic failover using fileshare witness.

Have you tried setting up Availability Groups within your environments?  I am curious to hear from you.

Thanks for reading.


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