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Asked: 2021-02-21 12:40:52 +0800 CST

SQL Server Always On Availability Group Zero Downtime Update Procedure

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Here I have a 2-node SQL Server 2016 AlwaysOn Availability Group cluster, with 1 primary and 1 secondary.

The question is - what is the optimal way to install Microsoft Updates on the servers in the cluster? I have struggled to find good, clear recommendations on this.

Here is my current thinking:

  1. Install updates using Microsoft Update on the secondary
  2. Restart the secondary to finish the updates
  3. Perform a manual failover from the Primary to the Secondary
  4. Install updates using Microsoft Update on the new-secondary (former primary)
  5. Restart the new-secondary (former primary)
  6. Perform a manual failover from the new-Primary to the Secondary, making the original primary the primary again

My understanding is that this will:

  • Cause absolutely no application downtime
  • Cause no syncing errors
  • Cause no data corruption
  • The cluster will not generate errors when half the nodes are updated and the other half are not

Is this correct? Is there a better way to do this?

Thanks in advance - any help is greatly appreciated.

sql-server high-availability alwayson sql-server-2016

1 Answers

  1. Best Answer

    Here's a step-by-step guide on how to achieve what you want:

    Apply SQL Server patches or cumulative updates in SQL Server Always On Availability Groups

    You might scroll down right to the "Preparatory Phase" section skipping all the "water".

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