I have just upgraded my firewalls to R80.10 version.
What would be the key indicators to be monitored?
The easiest things to monitor show in SmartConsole: the CPU and Memory usage.
The command cpview (from the CLI of the gateway) will also give you a bit more details.
See: CPView Utility
You may want to monitor other environment specific items like interface counters and the like (some of which will show in cpview).
I guess it's bit late to benchmark something if you already upgraded i would normally compare CPU (check each core not just average aggregate), memory just as Dameon said, plus concurrent connections, new connection rate, total throughput. Check also acceleration stats.
I find those good measurements to compare before and after. So you know upgrade has not had severe impact on your traffic.
There are more but this usually is enough
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