Most Microsoft software products – especially server products – can be licensed under multiple different models and metrics. SQL Server probably is the best example of a product that presents companies with multiple decision layers when analyzing new use cases:
– Commercial Hosting or Volume Licensing? Companies need to determine whether a particular use case requires commercial hosting rights or whether internal-use licenses under one of Microsoft’s volume-licensing programs are all that is needed. (Microsoft’s current guidance on commercial-hosting use cases is contained in the Services Provider Program Reference Card, available here.)
– For Commercial Hosting Use Cases, SPLA or Self-Hosted Applications? Microsoft offers commercial-hosting rights either under the Services Provider License Agreement program or under the Self-Hosted Applications benefit with Software Assurance. SPLA is a flexible model that entails monthly reporting based on current usage. The Self-Hosted Applications model requires a capital expenditure on licensing, but avoids the administrative burdens associated with monthly reporting.
– Licensing per VM or per Host Server? In virtualized environments, SQL Server licenses may be assigned either to individual VMs (“Operating System Environments,” or OSE in Microsoft lingo) or to the physical host servers on which those VMs are running. Licensing per individual VMs often makes more sense for less dense virtualization environments, but it often can be difficult to determine where to draw the line.
– Licensing per Cores or per CALs? SQL Server Enterprise may be licensed only based on the number of physical processor cores active on a server (or on the number of virtual cores allocated to an individual VM). However, SQL Server Standard may be licensed either based on cores or based on the number of servers plus the number of client users or devices requiring Client Access Licenses (CALs). Companies with heavy SQL Server usage across numerous users often can realize cost savings by licensing with cores – which allows for unlimited clients – but core licenses can be much more expensive than server licenses and CALs.