Licensing Microsoft Windows Server in SPLA and CSP Hosters
When you rent Microsoft Windows Server virtual machines from a service provider, those machines require licenses. There are always two perspectives on service provider licensing: the provider's perspective and the end customer's. We'll cover both in this quick reference guide.
Frequently asked questions
May end customers bring their own Windows Server licences (BYOL) to a provider?
Yes, via the Flexible Virtualization benefit except on "Listed Providers" (see notes below the table).
Dedicated hardware on "Listed Providers" – Amazon, Google, Azure, Alibaba – differs from all other providers ("Authorised Outsourcers"). You may only BYOL licenses bought before October 2019.
Flexible Virtualization Benefit excludes "Listed Providers".
Are Windows Server Client Access Licences (CALs) required in SPLA?
When you license Windows Server via SPLA, Windows Server CALs are not required. However, other types of Client Access Licences are required if you use any additionally licensed functionality of Microsoft Windows Server. Such licences in SPLA are called "Subscriber Access Licences" or SALs:
Windows Server Active Directory Rights Management SAL,
Windows Server Remote Desktop Services SAL,
Microsoft Identity Manager SAL.
Note that SALs are typically licensed per user but may also be per device.
IMPORTANT: This exception only applies to SPLA licences. Windows Server licenses brought to a provider or licences acquired from a CSP hoster require Windows Server CALs.
Are Windows Server Client Access Licences (CALs) required when we bring our own licences to a provider?
Yes. Windows Server licenses brought to a provider or licences acquired from a CSP hoster require Windows Server CALs.
May I bring my own RDS CALs to a provider?
Yes, that is allowed for RDS User CALs similar to Azure.
What Windows Server versions can I run in SPLA?
Any version. SPLA licences are always of the most current version. SPLA also includes downgrade rights.
Running out-of-support versions is compliant but ask your provider if they are willing to take security risks.
What are Windows Server editions available through SPLA?
SPLA licences are available in the following editions:
Windows Server Datacenter
Windows Server Standard
Windows Server Essentials
What license do I need for Windows Server Enterprise in SPLA?
To run a Windows Server Enterprise instance in SPLA, you must license it as Windows Server Standard.
That is because the Windows Server Enterprise edition was deprecated in 2012. The last released version was Windows Server Enterprise 2008 R2.
May I use Windows Server Datacenter licenses on a multi-tenant host?
Here are the two scenarios when it's permitted:
You are a provider. You may assign SPLA Windows Server Datacenter licenses to a host. You are permitted to run an unlimited number of virtual machines from multiple end clients on the licensed host.
You are an end client. You may bring your own Windows Server Datacenter licences to a third-party hosting except for Azure, AWS, GCP and Alibaba and assign them to your virtual machines. It is permitted both on dedicated and multi-tenant hardware. The licenses must be either subscription licences or licenses with active Software Assurance. You must also have enough Windows Server CALs that are either subscriptions or licenses with active Software Assurance.
Providers may not use any other Windows Server Datacenter licenses for hosting except for SPLA licences and eligible licenses brought by their end clients.
Cloud Solution Partner-Hoster. You may use installation media and activation keys granted to you by the CSP-Hoster program. When renting out the pre-built virtual machines to your end clients, you must ensure they have eligible licenses.
End clients may bring their existing licences, or you may sell them appropriate licenses with your services. Please remember that Windows Server BYOL also requires the end clients to have enough Windows Server CALs that are either subscriptions or licenses with active Software Assurance.
May I license Windows Server per virtual machine, like on-premises?
No, SPLA does not include the Windows Server per-VM licensing option. It is only available when end clients bring their own Windows Server licenses or purchase license-included services from a CSP Hoster.
Microsoft Windows Server licensing for providers
Calculating Windows Server Datacenter and Standard core SPLA licenses
The quantity of required Windows Server Datacenter or Standard SPLA licenses depends on the number of physical cores on the host (subject to change on October 01, 2022).
Count physical cores in each processor. Hyper-threading does not matter.
Assign the number of single-core licences equal to the number of cores in a processor but not less than eight.
Here's a formula for Microsoft Excel:
=MAX(8, CoresPerProcessor) * Processors
Pay attention that the price list item is a two-core pack. Therefore, to calculate the number of core packs to report to your SPLA reseller, use this formula:
=MAX(8, CoresPerProcessor) * Processors / 2
Windows Server Datacenter and Standard SPLA licenses in VMware, Hyper-V, and KVM
Regardless of the host's hypervisor, here are the basic rules:
For an unlimited number of virtual machines, assign Windows Server Datacenter licenses to the host.
Windows Server Standard licenses assigned to the host only permit running one virtual machine. Please note that it's not two virtual machines like in volume licensing.
Let's look at some advanced scenarios.
If you have a standalone host – not a cluster member – with multiple Windows Server Standard virtual machines, use this formula to calculate Windows Server Standard core packs:
=MAX(8, CoresPerProcessor) * Processors * VMs / 2
Pro tip: After approximately seven Windows Server Standard virtual machines on the host, Windows Server Datacenter core licenses become cheaper. The breakeven point for Core Infrastructure Suite is approximately four virtual machines. Check your price list.
If you have a low number of Windows Server Standard-only virtual machines in a cluster, it may also be cheaper to license it with Windows Server Standard. However, due to Microsoft demanding the hosts to be licensed for the maximum number of virtual machines, you need to multiply all licensable cores in the cluster by the number of Windows Server Standard virtual machines and then divide the result by 2 to calculate the number of core packs:
=SumOfLicensableCoresInTheCluster * VMs / 2
where for each host, licensable cores are:
=MAX(8, CoresPerProcessor) * Processors
Pro tip: After approximately seven Windows Server Standard virtual machines in the cluster, Windows Server Datacenter core licenses become cheaper. The breakeven point for Core Infrastructure Suite is approximately four virtual machines. Check your price list.
How to calculate Core Infrastructure Suite licenses in SPLA
All the rules for Windows Server (Datacenter and Standard) also apply to Core Infrastructure Suite (CIS).
How to calculate RDS SALs in SPLA
An access license is required for each authorised user regardless of their activity.
Find out what security groups are authorised to access Remote Desktop (not Remote Desktop Administration),
Count all persons in all those groups and nested groups (don't include service accounts).
Activity or inactivity of users does not affect the number of required client licenses in SPLA. If a person has access, they need a license.
The provider may deduct two users accessing servers for the sole purpose of testing, maintenance, and administration of products from this number. They don't require SALs.
How to calculate Windows Server licences brought by end clients?
Note: BYOL is severely limited if you are a Listed Provider. The below is for Authorized Outsourcers only.
When your end clients bring their own licences, they may be assigned in two ways:
To the hardware cores of servers dedicated to an end client,
To individual virtual machines on either dedicated or multi-tenant servers.
Assigning licences to dedicated servers is governed by Microsoft Product Terms because they are regular Volume or CSP licenses. It is a complex subject requiring a separate article.
When licensing individual virtual machines, make sure that the licences brought by your end clients or the licenses that you sell them with your services are either subscription licences or licences with active Software Assurance.
Here's an Excel formula to calculate the number of core packs for a virtual machine taking into account the compulsory minimum of 8 core licenses:
=MAX(8, VirtualCores) / 2
Bringing your Windows Server SPLA licenses to a different Data Centre Provider (DCP)
Windows Server core and processor licenses are not DCP eligible. The provider that owns the data centre must report Windows Server licenses through their SPLA.
All SALs are DCP eligible. A provider may report SALs through their own SPLA even if they deploy Windows Server workloads to a different Data Centre Provider.
IMPORTANT: DCP rights to Listed Providers will be revoked after September 30, 2025. Review your practices if you use Listed Providers as DCP, directly or indirectly.
Microsoft Windows Server licensing for SPLA clients
"Listed providers" are Amazon AWS, Google GCP, Microsoft Azure, and Alibaba. All the rest are "Authorised outsourcers".
From October 01, 2022, you have the following options:
Dedicated hardware in "Listed providers"
Dedicated hardware in "Authorised outsourcers"
Bring your own licences (BYOL)
Restricted (see notes below the table)
Dedicated hardware on Listed Providers differs from all other providers ("Authorised Outsourcers"). You may only deploy licenses bought before October 2019.
The licences you take (bring) to a provider are governed by Microsoft Product Terms.
Please bear in mind that we are not Microsoft, and this article is independent expert advice. There may be mistakes, omissions, and out-of-date and incomplete information. Always refer to Microsoft Product Terms for the official terms and conditions.
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