April 12, 2021 at 9:15 am
hi guys,
i have a 2 node AlwaysOn. i need some confirmation on the step on how to keep the service still up while u go about patching it.
just wondering is there a glitch or any disconnection from the applications services when i do a failover of the AOGP?
my data-transfer mode is synchronous-commit.
April 12, 2021 at 9:47 am
April 12, 2021 at 11:55 am
The failover will cause disconnects on the application side. That's unavoidable. However, the overall down time will be very small. In flight transactions will be lost. All committed transactions will be saved.
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June 9, 2021 at 6:53 am
since is unavoidable, how long a gap can i allow before doing a final patch on the Primary node, after a week ? ( while the rest of the secondary nodes are already in higher patch level)
June 9, 2021 at 7:01 am
You should really be keeping things insync, so I would do both nodes at the same time. You never know what will happen so if a patch fixes a bug and you fail back due to hardware/failure level conditions to an unpatched node your back in broken territory.
Your applications need to be using connection retry logic to keep polling for a connection should their existing one be broken. That way yes you will have a few seconds of downtime while the replicas switch roles but the end user is none the wiser.
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