How to perform Windows Update for SharePoint 2019 DB Cluster

That’s a good question and one that comes up often with SharePoint farms running on clustered SQL backends. Updating the Windows Servers that host your SharePoint 2019 databases requires some care, but as long as your HA (Always On / failover cluster) is configured correctly, patching one node at a time is the recommended approach.

A few key points to keep in mind:

✅ One node at a time – Patch the passive node first, failover if needed, then move to the other node on a separate maintenance window. This avoids downtime.

🔄 Failover testing – Before patching, make sure failover between nodes works cleanly. This will minimize any risk during updates.

🗂️ Backups – Always take a full SQL and SharePoint farm backup before applying patches.

🚦 Restart timing – You can restart after patching each server individually; SharePoint services will remain available as long as the cluster maintains quorum.

📋 Maintenance mode – Put the node under maintenance mode in Failover Cluster Manager (or suspend availability replica if using Always On AGs) before patching.

As long as you follow the proper sequence, SharePoint should continue to run without noticeable service impact while you patch the servers on separate days.