The statement that is true about upgrading the firmware on a Cisco MDS storage switch with dual supervisors is that the new firmware is load on the standby supervisor first. This is part of the non-disruptive upgrade process that allows the switch to continue operating while the firmware is updated. The standby supervisor receives the new firmware image and reloads with the new version, while the active supervisor remains in service with the old version. Then, a switchover occurs, making the standby supervisor the new active one, and the old active supervisor receives the new firmware image and reloads. Finally, the modules are upgraded one by one, starting from the lowest numbered module. The other statements are not true because:
* The standby supervisor does not need to be offline before the firmware upgrade begins. It can be online and in standby mode, ready to receive the new firmware image and reload.
* Both supervisors do not load the new firmware and then the active supervisor reboots. This would cause a disruption of service and a loss of configuration. The firmware upgrade is done in a sequential manner, with one supervisor at a time.
* Supervisors cannot be upgraded independently to test the new firmware. The firmware versions on both supervisors must match, otherwise the switchover will fail and the switch will not operate properly.
References: For more details on how to perform a firmware upgrade on a Cisco MDS storage switch, please refer to the following resources:
* How to Perform an MDS 9000 Series Switch Non-Disruptive Upgrade
* Cisco MDS 9000 NX-OS Software Upgrade and Downgrade Guide, Release 6.2(x)