i need to upgrade two R65 UTM-1 in a cluster and since I don't have two spare appliances, i'd like to verify the process..

I can afford a maintenance window with a downtime allowed, based on these facts i suggest:

1) Disconnect the appliances (shutdown the interface for synchronization)
2) Upgrade 1st appliance to R70.x
3) Upgrade 2nd appliance to R70.x
4) Connect the appliances again

Is this scenario correct?

Question 2:

What is the best way to build a HA management on these appliances, during this upgrade process - considering there is only one management running on the primary appliance.

Thank you.