Understanding Microsoft server licensing can be tricky. Each Microsoft server product follows one of four basic licensing models, which you need to know before you start.
(You potentially also need to know about CPUs and OSE licensing rules – there’s a bit on that at the bottom of this article.)
To help you make the right choices when you plan your own server implementation, here’s a brief overview of the four server licensing models:
1. Per core/CAL
Two main things you need to know:
- You need multiple processor cores (a.k.a. server-core licences) to get a core-based server to work.
- Servers using the ‘per core/CAL’ model also require client access licences (CALs), which connect users/devices to the server(s).
Each of Microsoft’s core-based server products require a different number of core licences to work. Product descriptions on tt-exchange state the exact number.
Important for charities: each time you request a core-based server licence donation through tt-exchange, you get two processor cores.
So if you want Windows Server Standard, for example, the first thing to do is check how many core licences you need (you need 16). Assuming you’re registered on tt-exchange and are eligible for Microsoft donations (check eligibility here), that means you should place 8 donation requests — i.e. 8 (donation requests) x 2 (core licences) = 16 (total core licences).
The CALs you’ll need are separately available through tt-exchange too.
As opposed to a core-based server, you only need one server licence for your product to function under this model. You still need CALs though, just like above.
For products like those, you only get one server licence for each donation request you place through tt-exchange, as that’s all you need.
3. Per core
This model uses core-based server licenses but doesn’t require CALs.
Just like the ‘per core/CAL’ model, each core-based server licence donation requested through tt-exchange gives you two processor cores. Product descriptions tell you how many processor cores you need.
BizTalk Server is an example of a product using this model.
Some other server products, like SQL Server, can be licensed in either the Server/CAL or Per Core (Core-Based) model. You can work out which licensing model each server product uses by looking at the product name and by checking whether CALs are available for that server on tt-exchange.
4. Management servers
Management servers let you manage other machines. You get management licenses (MLs) when you’re using them to manage servers and you get client MLs when you’re managing non-server operating system environments (OSEs).
System Center products use this model. The software you need to run the server is included with MLs and client MLs.
MLs (the ones for managing servers) work more like the core-based model than the server/CAL model — you need multiple licences to get the server up and running, Microsoft set a minimum for each server product, and each server ML product donation on tt-exchange is valid for two processor cores.
Client MLs (the ones for non-server environments) work more like the server/CAL model – you get one licence for each donation request you make through tt-exchange, and only one is necessary for each OSE you manage.
OSEs and server software
Server operating systems and server applications can either run in physical or virtual operating system environments (OSEs).
If you want to run servers across multiple OSEs, you should check the OSE licensing requirements carefully before you begin.
The reason is that many Microsoft server licenses can only be used for a single OSE. If you want to install one of those licences on more than one OSE on a single computer, you’d need separate licences for each environment.
That said, some of Microsoft server licenses can be used in more than one environments (confusing, huh!).
Microsoft have a bit more detailed information on different server licences here.
Processors and servers
One final potential complication – a short word on CPUs: you need to know how many processors your machine has for some core-based server software.
Windows Server Standard, for example, will run with 16 core licences on a computer with 1 or 2 processors. It requires you to have at least 8 core licences per processor though, so if you have 4 processors, you’d need 32 core licences to get it working.
Click here to see the list of donated Microsoft products available to charities through tt-exchange.
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