Best way to upgrade redundant pair

It seems like there has been some conflicting information over the years on the best (least downtime) method to upgrade a redundant pair. It used to be recommended to upgrade the Master first. This was because the project state would be Incompatible if the Backup was upgraded first and clients tried to switch over.
https://inductiveautomation.com/forum/viewtopic.php?f=70&t=7760&start=0&st=0&sk=t&sd=a&hilit=project+incompatible

Recently, I’ve seen a support topic from Travis that recommends upgrading the Backup first and transfer clients over to the Backup after its reconnected. Then, upgrade the Master.
https://support.inductiveautomation.com/index.php?/Knowledgebase/Article/View/86/0/upgrading-or-patching-a-redundant-ignition-pair

I just tried this with an upgrade from 7.7.3 to 7.7.4 and sure enough the clients wouldn’t transfer to the Backup after it was upgraded because it the project state was Incompatible. Am I missing some kind of override settings or something?

We just had a similar experience with this. The first time we tried the upgrade, we started with the Backup system. We had several issues as a result. After finding the conflicting information on the Inductive web site about upgrading redundant systems, I called Travis to get verification on which method to use. His suggestions were based on our system (We upgraded from 7.7.2 to 7.7.4):

  1. Force a failover to the Backup system (A web link for this is located on the Status page)
  2. Once the Backup system has taken over, upgrade the Master system.
  3. Once the Master system is back online and the Master system has taken control, upgrade the Backup system.

This process worked for us.

You may want to confirm this with Tech Support.

Chris

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Thanks Chris. We will try that method on the next upgrade.