How Architecture Can Impact Licensing

How architects design systems to run SQL Server workloads can have a huge impact on licensing. In the following hypothetical example involving the same nine SQL Server Standard edition instances, all clustered for high availability, between four and nine Standard edition processor licenses are required, depending on architecture.

The three scenarios illustrated are based on the following assumptions:

• All nine SQL Server Standard edition instances are roughly comparable in terms of systems resources consumed
• The instances are hosted on three servers, each with two physical processors containing four cores (for a total of eight cores)
• Each server has sufficient system resources to run up to six of these instances at the same time with acceptable performance (although it’s preferable to run three to five instances)
• Windows Server failover clustering is used to provide high availability in the event one of the three servers fails.

In scenario 1, three active SQL Server instances (dark background) are run on each host server’s OS alongside three passive failover instances (light background), which pick up workloads if one of the other servers fails. For example, a failure of Server B—which hosts instances 4, 5, and 6—causes Server C to pick up instances 4 and 5, and Server A to pick up instance 6. Since Microsoft does not charge extra when multiple independent SQL Server instances share the same OS and each server has two physical processors, a total of six SQL Server Standard processor licenses are required (two per server).