Hi
we’re running 2 Peplink Balance 380’s in High availability mode. Both devices run on Firmware 5.4.9. We would like to upgrade to the latest but it’s almost impossible to take both devices offline at the same time. Even the time it takes for the slave to take over isn’t preferred during business hours.
Is it save to take one offline during the evening or weekend, upgrade it to the latest firmware and bring it back online the following night and repeat the process with the other peplink? Or will the difference in firmware cause trouble with High Availability?
I’m just another customer, and I may be telling you something correct here. If so I’m sure someone from Peplink will be along to correct me 
“High availability” and “configuration sync” are actually two separate features.
What we do is disable config sync but leave HA in place. Then we upgrade the firmware on the passive device, failover, upgrade the other device, fail back, and re-enable config sync.
There doesn’t seem to be any problem with high availability working properly between different firmware versions. It is safe to wait as long as you need to before upgrading the second device.
Please reference this post for High Availability (HA) router pair firmware upgrade procedures.
