What is SQL Server AlwaysOn?

SQL Server AlwaysOn is the new high availability and disaster recovery solution for the next release of SQL Server. Using AlwaysOn businesses can achieve increased application availability for their mission critical applications and get higher returns on their high availability investments through better utilization of hardware resources. AlwaysOn also increases productivity and lowers TCO by greatly simplifying high availability deployment and management.

Database Availability and Instance Availability using AlwaysOn

The key aspect of AlwaysOn is that it provides you with the flexibility to configure high availability and disaster recovery for your application databases and\or for the entire instance

  • AlwaysOn Availability Groupis the new feature in SQL Server AlwaysOn that provides availability for application database(s). Availability Group provides a rich set of options that gives the flexibility to configure a high availability environment that can meet the SLA's of the various applications in your environment. The feature also comes with a set of options that allows utilization of your secondaries. Apart from these options there is complete integration with management studio and Powershell that makes deployment and management of Availability Group extremely simple.

  • AlwaysOn Failover Cluster Instance enhances the existing SQL Server Failover Clustering feature and provides availability for the entire instance. AlwaysOn provides a richer set of capabilities that will increase instance availability and addresses a number of existing pain points.

Key Features of AlwaysOn Availability Group

  • Multi database failover
  • Multiple secondaries (A secondary is conceptually similar to a Mirror in Database Mirroring)
    • Max of 4 secondaries
  • Synchronous and asynchronous data movement
    • Support for 2 synchronous secondaries for additional data protection
  • Built in compression and encryption of transport
  • Automatic, Manual and Forced Failover
  • Flexible failover policy
  • Automatic Page Repair
  • Active Secondary
    • Readable secondary
    • Secondary backup
  • Automatic application redirection using virtual name
  • Configuration Wizard for simplified deployment
  • AlwaysOn Dashboard
  • System Center Integration
  • Automation using Powershell
  • Rich diagnostic infrastructure
    • DMV, Perfmon Counter, Xevents etc…

 
Key Features of AlwaysOn Failover Cluster Instance

  • Native support  for multi-site clustering across subnets enable DR using failover cluster instances
  • Flexible Failover Policy
    • Providing new failure detection mechanism using sp_server_diagnostics
    • Customer Configurable failure condition level for more granular control on failover
    • Better diagnostics
  • SMB support  enabling consolidation of more than 26 instances
  • Support TEMPDB on local drive
  • AlwaysOn Failover Cluster Instance can be a part of an AlwaysOn Availability Group

 

Additional Resources

For more information on AlwaysOn please go to the AlwaysOn Resource Center. This has links to AlwaysOn Team blog, forum, documentation, download etc.

Also feel free to look at the 2011 TechEd sessions on AlwaysOn which contains videos and demos on AlwaysOn  – Introduction session & Drill Down session.

Please download SQL Server Code Name “Denali” CTP3 today and play with the AlwaysOn features. We are eagerly looking forward to feedback on the product, which you can provide to our engineers directly on our Connect Site.


Santosh Balasubramanian
Senior Program Manager
Microsoft SQL Server Engine Team