Per Core Licensing

When it comes to licensing software, understanding the licensing models and requirements is crucial to ensure compliance and avoid overpayment. Microsoft's Per Core Licensing offers a versatile approach to licensing, accommodating various computing environments. This article will focus on Per Core Licensing for Microsoft products like SQL Server and Windows Server.

Basic concept Per Core licensing

The Per Core licensing model, introduced in 2012, requires the purchase of licenses per core based on physical processor and/or cores. Core-based licensing is a consistent licensing metric, whether a server is deployed on-premise or in hybrid/cloud environments. The exact requirements may differ between the various server software license requirements. When opting for the Per Core model you don’t need additional CALs if users or devices connect from inside or outside a company's firewall.

There are three main concepts within Per Core licensing, namely:

Physical Server: The actual entire hardware system that runs the server software.

Physical Processor: The physical chip in the socket contains multiple physical cores.

Physical Core: A small processing unit within the physical processor of the physical server.

SQL Server Per Core licensing

SQL Server utilizes the Per Core licensing model, which allows you to license based on the number of physical cores on a server or the number of virtual cores supporting virtual machines running the software. All physical cores must be licensed for physical servers, while virtual machines require licensing all virtual cores. A minimum of 4 cores need to be licensed per physical processor, a core license is required for each core. These minimum requirements may differ in rare cases, as noted in official documents.

Calculation examples by core licensing SQL Server

Below are some example calculations for different scenarios.

Licensing physical SQL Server

When licensing according to the Per Core model every core in every processor of the OSE running the SQL server software needs to be licensed. Every physical processor needs at least four core licenses. It’s also worth noting that the core licenses are sold in packs of 2.

Example 1. Three physical servers are running SQL services that need licensing.

Physical server 1 is running 2 physical processors with 2 physical cores. The rule is that every physical processor needs to be licensed with at least 4 core licenses, even if there is less than 4 physical cores in the physical processor. In this case that would mean that both processors need 4 core licenses, making a total of 8.

Physical Server 2 is running 

Licensing individual SQL Server Virtual Machines (VMs)

Example 2. There are three virtual machines with the following number of virtual cores:

Virtual machine 1. 2 Virtual cores (Minimum of 4 cores need to be licensed)

Virtual Machine 2. 4 Virtual cores

Virtual machine 3. 6 virtual cores

Each virtual core needs to be licensed, but even here the minimum of four licenses per virtual machine applies. Therefore, the calculation of the total number of required licenses is not 2 + 4 + 6 but 4 + 4 + 6. In this example, the total number of licenses needed is 14.

In versions of SQL Server 2022 or later you need to have Software Assurance or a subscription to license virtual machines.

Licensing individual containers SQL Server

Example 3.

In versions of SQL Server 2022 or later you need to have Software Assurance or a subscription to license individual containers. In this example, a company wants to license 2 containers with 4 virtual cores per container.

This would need 8 core licenses (2 containers x 4 cores per container = 8 total virtual cores).

Windows Server Per Core licensing

In its Standard and Datacenter editions, Windows Server also employs the Per Core licensing model. Like SQL Server, you can license based on physical or virtual cores. However, Windows Server also offers the option to license using the Per Core/CAL (Client Access License) model. With Windows Server Per Core licensing a minimum of 16 licensed cores are needed, this is labeled as a ‘base license’. Additional cores can be licensed with 2-core or 16-core packs.

Calculation examples per core licensing Windows Server

Licensing physical Windows Server

This example will give an example for licensing 16 cores.

Core licenses are sold in packs of 2. So, for 16 cores, you need 8 licenses (16 cores / 2 cores per license pack), or one 16-core pack.

Licensing Windows Server Virtual Machines (VMs)

This example will give an example for licensing 4 virtual cores.

Windows Server 2022 has a minimum core requirement of 16 cores per virtual machine. Even if your virtual machine has fewer than 16 cores, you'll need to license for a minimum of 16 cores. Core licenses are sold in packs of 2. For a virtual machine with 16 cores, you need 8 licenses (16 cores / 2 cores per license pack).

Benefits of the Per Core licensing model

Per Core Licensing offers several benefits for organizations. These include:

Flexibility: Per Core Licensing allows organizations to easily scale their computing environments by adding or removing cores without the need for additional licenses.

Consistency: The Per Core model provides a consistent licensing approach across different environments, including physical servers, virtual machines, and the cloud.

Simplified Management: With Per Core Licensing, organizations do not need to purchase additional Client Access Licenses (CALs) for users or devices accessing the server software.

Cost Efficiency: Organizations can optimize their licensing costs and avoid overpayment by accurately licensing the required number of cores.

Per Core Licensing offers flexibility, consistency, simplified management, and cost efficiency for organizations using Microsoft software products.

Compliance of Per Core licensing

To ensure compliance, perform regular assessments of your computing environment, calculate the required licenses accurately, procure licenses through authorized channels, maintain proper documentation, and stay updated on any changes in Microsoft's licensing policies. Read more about Software Asset Management and Microsoft licensing rules here.