Backups and Restores Using Availability Groups
With the release of Microsoft SQL Server 2012, a whole new mechanism for ensuring continuous availability of databases in your system was introduced: AlwaysOn Availability Groups. Availability Groups provide a mechanism for failing over a database, or a group of databases, from a primary replica onto between one and four secondary replicas. This ability to keep a database online with little to no data loss and without the requirements of the old Failover Cluster shared disks and matching hardware makes for a great way to help ensure the continuity of access to data in your systems. Further, secondary replicas can be set up as read-only replicas, allowing you to offload some of the data access from your production system, hosting the primary replica, to one or more of the secondary replicas. If all this isn’t enough, you also get the ability to remove the server load required for running part of the backup process and put that into the secondary replicas as well. The ability to change where and how you back up your databases without negatively affecting your ability to recover a database is a major improvement in the capabilities available for disaster recovery, and it provides performance improvements.
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