The three building blocks of server licensing
A complete Windows Server license consists of three building blocks. The first is the core licensing of the server itself. With Standard and Datacenter, licensing is based on physical processor cores. Microsoft sets a minimum purchase per server, regardless of the actual number of cores. If a server has more cores, correspondingly more core licenses are required.
The second building block is the CALs, the Client Access Licenses. Every user or every device that accesses the server needs a CAL. The third building block concerns virtualization: the edition determines how many virtual instances a license covers, two with Standard, unlimited with Datacenter. Essentials combines this logic in simplified form into a single edition.
How to determine your licensing needs
- Inventory the hardware. Number of physical processors and cores per server. From this, the required number of core licenses follows.
- Count the access. Number of users and accessing devices. The smaller number determines the more cost-effective CAL type.
- Plan the virtualization. Number of planned virtual machines per host. It decides between Standard and Datacenter.
- Check the RDS special case. Anyone using Remote Desktop Services adds RDS CALs in addition to the normal CALs.