How to avoid a double reboot when doing a Sophos XG Firmware upgrade?

Hi - I have 2 550 firewalls in HA and at one point years ago I think I uploaded a .sig firmware file and did the upgrade that way which ended up rebooting both firewalls at once.  Since then I just wait till there's a popup window saying there's an update, and proceed to download and install without doing a manual upload.

We're not ready to move to v19 of the firmware, and would like to move from 18.5.2 to 18.5.4, which does show up on the firmware tab in the GUI.  So does the v19 firmware as well.  It doesn't seem like it should make any difference clicking install to the 18.5.4 firmware vs. the v19 when it comes to the HA and how the upgrade process works.  I would expect it to reboot one at a time.

To me - the documentation isn't really clear on what actions will cause both firewalls reboot at once.  I'm used to a few seconds of outage for these tasks, and want to avoid a 25 minute outage.

Can anyone clarify this for me? I don't want to be surprised by a large outage.


Edited Tags
[edited by: Erick Jan at 11:19 PM (GMT -7) on 3 Oct 2022]