Implementing High Availability and Workload Balancing Using SQL Server AlwaysOn Availability Groups

SCS designed a new platform, EDEN 3.0, incorporating AlwaysOn Availability Groups as part of the solution. AlwaysOn provides Enterprise-grade high availability and load balancing by creating readable, real-time transaction synchronized secondaries. With EDEN 3.0, the readonly API calls could now be rerouted to the AlwaysOn secondary via the listener service, while the eLink batch process executed against the writeable primary. The read-only API calls would then return data from the snapshot isolation level secondary instance with no locking issues during processing. The only code changes required for this implementation were appending ApplicationIntent = READONLY to the API connection string.

SCS also designed a migration strategy for the existing environment that eliminated the need for bulk migration and EDI and instead leveraged distributed database views. The distributed views allowed for T-SQL statements to be simultaneously executed against the new and legacy platforms with minimal performance impact. Data inserts and transfers were then handled logically in the view definition, rather than using triggers to route changes to the appropriate legacy or EDEN 3.0 model. The query statements issued from the EDEN client, PowerLink, then required no refactoring as a result of this architecture design, with the source views being completely transparent to the calling applications.