We currently have a set of ASA5520's in resilient failover mode and wish to upgrade them to 5550's. The problem is we would like to have no downtime of the Firewalls.
I have an idea of replacing the the Standby first with a 5550 and bringing on line with the Primary 5520. Then failing over to make the 5550 Primary and the 5520 Secondary. Then upgrade the Secondary 5520 to a 5550. Leaving us with a succesfull upgrade to ASA5550's and no down time.
Has any one done this or can see an issue with this type of upgrade path.