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Steps for Rolling AG Upgrade with new VM's (2016 OS & SQL)

Brian Tobin 0 Reputation points
2026-01-23T00:02:31.8433333+00:00

I found the steps for a rolling upgrade of a 2 node AG in place, however I wish to also Upgrade o/s..

Are the steps any different if we add a new upgraded VM to the cluster & join it to AG, then Failover DB from Primary to this New server. Next add another upgraded Server. Finally Decomm the two older VM's

Many Thanks

Brian

SQL Server Database Engine
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Answer recommended by moderator

Lakshmi Narayana Garikapati 1,315 Reputation points Microsoft External Staff Moderator
2026-01-23T11:31:53.1266667+00:00

Hi Brian.,

Thanks for the reaching out to SQL Forum

The steps are different when you’re upgrading the operating system in‑place rolling upgrades are fine for SQL patching, but OS upgrades are best handled by introducing new nodes.

The recommended approach is:

  • Build new VMs with the upgraded OS and the same SQL Server version/patch level.
  • Join them to the existing Windows Failover Cluster and configure them as secondary replicas in the AG.
  • Synchronize databases and validate health.
  • Fail over the AG to one of the new nodes once you’re confident everything is working.
  • Add the second new VM to the cluster and AG, then repeat the sync/validation.
  • Decommission the old nodes once the AG is stable on the new servers.

This method avoids the risks of in‑place OS upgrades on cluster members, gives you rollback safety, and keeps downtime minimal. Just make sure the cluster functional level supports mixed OS versions during the transition and confirm licensing before cutover.

https://learn.microsoft.com/en-us/sql/database-engine/availability-groups/windows/upgrading-always-on-availability-group-replica-instances?view=sql-server-ver17&redirectedfrom=MSDN

Thanks ,

Lakshmi.

 .

 

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  1. AI answer

    2026-01-23T00:02:41.4+00:00

    When performing a rolling upgrade of an Always On availability group (AG) while also upgrading the operating system, the process involves adding new upgraded virtual machines (VMs) to the cluster and joining them to the AG. Here are the general steps you can follow:

    1. Prepare the New VMs: Set up the new VMs with the upgraded operating system and SQL Server version.
    2. Join New VMs to the Cluster: Add the new VMs to the existing cluster.
    3. Add New VMs to the AG: Join the new upgraded VMs to the availability group as secondary replicas.
    4. Failover Databases: Perform a manual failover from the primary replica to one of the new upgraded VMs. This will make the new VM the primary replica.
    5. Upgrade Additional Servers: Repeat the process for the second new upgraded VM by adding it to the AG and failing over databases as needed.
    6. Decommission Old VMs: Once all databases are successfully migrated and the new VMs are functioning as expected, you can decommission the older VMs.

    It's important to verify synchronization at each step and ensure that your synchronous-commit replicas are synchronized before proceeding to the next step. This approach minimizes downtime and maintains high availability during the upgrade process.

    References:

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