Microsoft SQL Server - license requirements with virtualization
Overview
Product Licensing Terms
Microsoft's product terms stipulate that Microsoft SQL Server can be licensed per Server and per Core. In both ways, licensing differs between licensing by physical or virtual machines. However, Microsoft determines that licenses must be assigned to a "server" which is defined as: "Server means a physical hardware system capable of running server software":
This fundamental detail often leads to confusion when talking about "Licensing by Individual Virtual OSE". Users expect, that license requirements created from installations in virtual machines stay effective and there is no consolidation towards the physical host. However, Microsoft is quite clear in the terms, that the "(physical) server" must be licensed also in this case. That is why license requirements are automatically consolidated on the physical hosts. This is called "License Assignment" and described in detail below.
After assignment of the license to the physical server, the calculation of the required licenses implements either "licensing by physical core" or "licensing by individual virtual OSE" options. Which option is effective, depends on the license model of the license requirement.
| License Model | Option: Licensing by Physical Core | Option: Licensing by Individual Virtual OSE |
|---|---|---|
| SQL Standard ... | Never applied because not eligible by Microsoft product terms | Always applied |
| SQL Enterprise ... | Applied, if quantity of required licenses is lower than other option | Applied, if quantity of required licenses is lower than other option |
The application of the appropriate option is made automatically by the license model. Please see the examples below.
The license model also considers automatically, if the "license mobility" right can be applied.
The exercise of assigning licenses to the physical server based according to product terms is the reason why "License Mobility" is a topic. The assignment of the license(s) to the physical server is binding for 90 days, according to the terms. If a virtual machine is moved to another physical host within this period, both servers have to be licensed - the old and the new one. This minimum entitlement period does not apply, if the licenses used for entitlement are under active software assurance.
Example: Licensing by Individual Virtual OSE
- Host machine with 16 physical cores
- Two virtual machines each with 2 assigned cores and SQL Server Standard or Enterprise installed
- Licensing per Core
With SQL Server Standard, "Licensing by Individual Virtual OSE" is the only option. With SQL Server Enterprise, "Licensing by Individual Virtual OSE" is the better option compared to "Licensing by Physical Core on a Server" (because then it would require 16 core licenses). However, in both cases licenses must be assigned to the (physical) "server".
While minimum licensing of 4 cores per OSE applies, each virtual machine requires 4 core licenses. That is why the host must be licensed with 8 cores.
| License Requirement Status | Virtual Machine #1 | Virtual Machine #2 | Host |
|---|---|---|---|
| License Required | 8 Cores | ||
| Consolidated (License Assignment) | 4 Cores | 4 Cores |
Example: Licensing by Physical Core on a Server
- Host machine with 16 physical cores
- Two virtual machines each with 10 assigned cores and SQL Server Enterprise installed
- Licensing per Core
This option is only eligible with SQL Server Enterprise. Here as well, licenses must be assigned to the (physical) "server".
| License Requirement Status | Virtual Machine #1 | Virtual Machine #2 | Host |
|---|---|---|---|
| License Required | 16 Cores | ||
| Consolidated (License Assignment) | 10 Cores | 10 Cores |
License Assignment
Overview
Creating a license requirement for the eligible consumer is called license entitlement. At the same time, license requirement for technical consumer is consolidated with reason "License Assignment".
For SQL servers installed on virtual machines, the following license entitlement logic applies:
- The fingerprint is used to detect an SQL Server installation on a virtual machine "A" and entitle respective license requirements.
- The system checks the used license model and consolidates (cancels) the license requirement for the virtual machine, since licensing must be done for a physical device.
- The system creates a license requirement for an SQL Server and references the consolidated license requirement for the virtual machine as foundations.
License Requirement for the Virtual Machine
This license requirement for a virtual machine has been consolidated within the license entitlement.
On the Consolidation dialog page, users can view for which physical computers (current or former hosts of the VM) license requirements have been created.
License Requirement for the Physical Server
The license requirement for the host lists the underlying license requirements for virtual machines to ensure 100% transparency of correlations.
The following diagram illustrates the automatic license entitlement process:
This logic is used for all virtualized SQL servers, although ultimately, only a physical host requires an effective license. The license model used for this host defines an amount of required licenses based on the metric, the scope of virtualization permitted for one license and the license mobility.
