Vsan The construction of the world is long as you say yes.
Sorry, but what do you mean with that ?
We are not sure what was the component status before upgrade, if you are doing the upgrade/update on all hosts continuously without checking the resync statue , it may lead to this situation. again for 30 min 3.5TB data resync is bit high and in my guessing, I think there was pending resync before you started with this host update.
You have RVC command to check the component status and resync status and it is recommended to run and check the status often while updating multiple hosts.
- Why was 3.5TB needed to resync (which took 8+ hours)
Reason is given above
- Where is the event shown that my vSAN automatically rebuilding because my host was more then 60 minutes in maintenance.
vSAN will automatically rebuild, it is the behavior of the product so no event will be generated for that, you may run commands to check the status
- Based on my experience above, why should I use "ensure availability"?
Ensure accessibility will check if there is minimum level of component availability to run the vms fine. this process will check all the component state and create a missing component before entering the host into maintenance mode.
In case of full data migration it will take more time based on the amount of data residing on the host which is to be placed in maintenance and based on the storage policies.