Next SQL Server Improves Replication, Availability

SQL Server “Denali,” delivered as a Community Technology Preview (CTP) in Nov. 2010, provides a new infrastructure for replicating databases from server to server, called AlwaysOn Availability Groups. This new infrastructure seeks to meet customer needs for increased server uptime (high availability) and rapid, reliable recovery in the event of catastrophe (disaster recovery) by simplifying configuration and management and broadening the capabilities of the current SQL Server database mirroring technology.

High Availability and Disaster Recovery

Two common requirements of any critical database are high availability and disaster recovery. Though similar, their objectives are different in order to guarantee service.

High Availability

High availability is provided by a secondary source of data, which is ready should the primary source become temporarily unavailable due to server load, hardware failure, or a scheduled update. The former primary source remains generally available at some time in the future to resume the primary role or assume the secondary role. A key aspect of high availability is providing the switchover (failover) to the secondary source with as little downtime as possible. Availability measures are generally calculated as a percentage uptime per year, with the percentage of time closest to 100% being the desired goal.