Server Licensing

Question

We are building a disaster recovery site and are planning on replicating a few Microsoft virtual machines to the DR site and want to know if we will also require Windows Server and SQL Server licenses for the DR site?

The servers at the DR site are only replicas of the production servers and will remain offline until needed.

Answer 1

Hi Renrick,

I see the automated Q&A Assist bot gave you a solid overview of the SQL Server side of things, but it completely left you hanging regarding the Windows Server OS! Navigating Microsoft licensing for Disaster Recovery can definitely feel like a maze, so let's break down exactly what you need for both.

The short answer to whether you need licenses for the DR site is: It entirely depends on whether you have active Software Assurance (SA) and what your underlying DR hardware looks like.

Here is the practical, real-world breakdown:

1. SQL Server (The Application Layer)

The bot was spot on here. If your primary SQL Server licenses have active Software Assurance (SA) or are subscription-based, Microsoft grants you "Failover Rights." This means your offline, passive replica at the DR site does not need an additional SQL Server license. However, if you bought those SQL licenses outright (perpetual) without SA, you technically must fully license that passive DR instance.

2. Windows Server (The OS Layer)

This is where the rules change, and it's the part the AI missed. Unlike SQL, Windows Server is licensed at the physical hardware level (per physical core).

Even if those replicated VMs are completely powered off and just waiting at your DR site, the physical host servers at that DR location must be fully licensed with Windows Server cores to support them when they do turn on. Microsoft generally does not offer a "free passive" on-premises license for the base Windows Server OS. (Note: The only major exception is if your DR site is in Microsoft Azure, where you can leverage specific Azure Hybrid Benefits for Disaster Recovery).

In summary: You will almost certainly need to buy Windows Server licenses for the physical hosts at your DR location. For SQL Server, you are safe and don't need extra licenses only if your primary site has active Software Assurance.

I highly recommend checking with your IT procurement team or Microsoft reseller to verify your Software Assurance status before spinning up the DR site.

I hope this fills in the blanks the AI left behind! Please let me know if you need any more clarification on how the core licensing math works.

Tracy.

Answer 2

For SQL Server, a disaster recovery (DR) replica can be license-free if it meets the passive-instance criteria and the environment uses the supported licensing benefits. The key points from the provided context apply to SQL Server only (not Windows Server):

1. A passive SQL Server instance used only for standby/failover can be license-free if all of the following are true:
   • License mobility through Software Assurance is in place for the active SQL Server license.
   • The DR instance is strictly passive: it does not serve SQL Server data to clients or run active workloads. It is only used to synchronize with the primary and keep the database in warm standby.
   • Only allowed activities run on the secondary: CheckDB, full backups, log backups, and monitoring resource usage. Brief DR tests with both primary and DR running are allowed every 90 days.
   • The active SQL Server license covered by Software Assurance allows one passive secondary with up to the same compute as the primary.
   • The secondary SQL Server VM in Azure is configured to use the Disaster Recovery (DR) license type in the Azure portal.
2. For SQL Server on Azure VMs with Software Assurance or pay-as-you-go:
   • Free passive DR replicas are available when configured correctly as passive replicas (for example, Always On availability group secondaries that meet the passive criteria and have no active user connections).
   • Non-readable secondaries or readable secondaries with no active user connections qualify as passive DR replicas; any secondary with active user connections does not.
3. For Azure SQL Managed Instance:
   • A secondary managed instance used only as a passive DR standby (no read or write workloads) can use license-free DR replicas via the Hybrid failover rights or Failover rights benefits. vCore licensing for the secondary is not charged, but compute and storage are still billed.

The context does not provide rules for Windows Server licensing at the DR site, so no statement can be made about Windows Server licenses based on this information.

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References:

• Frequently asked questions for SQL Server on Azure VMs
• Business continuity and HADR for SQL Server on Azure VMs
• Manage licensing and billing of SQL Server enabled by Azure Arc
• Overview of business continuity with Azure SQL Managed Instance
• Disaster recovery with Managed Instance link - Azure SQL Managed Instance
• Overview of the Managed Instance link

Answer 3

Are Windows Server licenses needed for a disaster recovery replica?