This article describes the High Availability (HA) concept / rollback function.
During the Up2date process for Clusters and HA installations, you can set a unit to remain in reserve that will not be updated immediately along with the rest of the nodes.
This prevents you from having to manually unjoin a node from HA (to account for disaster handling) should you encounter an error when updating your UTMs.
Known to apply to the following Sophos product(s) and version(s)
Sophos UTM v9
What To Do
Prior to updating, on the Management | High Availability | Configuration screen, check the 'Keep node(s) reserved during up2date' box.
When the Up2Date is complete, you can re-add the reserved node to the cluster by clicking 'Upgrade Node', at which point it will be automatically updated.