Introduction
There are several high availability disaster recovery (HADR) solutions supported in SQL Server with the different versions that you may be familiar with or have implemented in your environments, such as transaction log shipping, database mirroring, and transactional replication. On the Windows server-side, you can also use Windows Server Failover Clustering (WSFC). This chapter focuses on AlwaysOn.
SQL Server AlwaysOn is meant to replace database mirroring, which was deprecated in SQL Server 2012, and addresses the limitations that database mirroring faced. Some of the commonly cited limitations of database mirroring include the following:
- Having only one unreadable mirror
- Inability to failover multiple dependent databases as groups
SQL Server AlwaysOn addresses these shortcomings. AlwaysOn is an Enterprise-only feature that leverages Windows Server Failover Clustering and provides some of the following benefits:
- An AlwaysOn configuration can have up to four readable secondary...