10 node AFF Netapp cluster nodes highly utilized and unable to set maintenance window for upgrade

[Pkjnetapp]

10 node AFF Netapp cluster nodes highly utilized and unable to set maintenance windo for ONTAP upgrade.

Hi friends,
Need your valuable suggestion as always.
I have a 10 node cluster which is highly utilized all times. Among those 2 nodes are hitting 80% on regular basis. As this a critical cluster I am unable to set a maintenance window for ONTAP upgrade. Vol move activity are not possible at the moment as need to upgrade cluster by next week. Any valuable suggestions please let me how to proceed with maintenance window. Is there any critical parameter like IOPs, latency which I can look into for performance and decide to set maintenance window. It should be non disruptive upgrade and Host team should not have any downtime during the activity. ONTAP Version upgrade planned from 9.11.1p8 to 9.11.1p16 to 9.15.1p16,it is a multi hop upgrade.

[yuls]

9.11.1P8 to 9.15.1p16 can be done just in one upgrade, don't need to upgrade to 9.11.1p16. It will save you time and will require less reboots.
It can be done non disruptively, just to make sure that all checks and preparation are done before upgrade. You can follow Netapp Documentation page or request upgrade Advisor plan if you are using AIQDigitalAdviser
here is link to documentation page https://docs.netapp.com/us-en/ontap/upgrade/automated-upgrade-task.html