Thank you for the information.
I have checked internally and found that the following parts have been changed in time.
-With the new RTFI (uRTFI), the backup is no longer performed before the upgrade, but instead is rolled back.
-Parallel Threading in Cluster Failure Checking.
-Improved cache flushes on upgrades.
We also saw in the ActiveIQ Event log that the following times.
Depending on the number of iSCSI sessions, it could take longer.
24 node production cluster went from 26 hours in 10.x to 11 hours in 11.x, will be 6 7 hours in 12.x.