Hello everyone,
Today I will share with you how to upgrade a stack of CE series switches.
You are advised to upgrade a stack in a fast upgrade mode. This mode shortens traffic interruptions by performing a master/standby switch switchover to upgrade the stack system.
During the upgrade, the standby switch first restarts with the new system software. After the upgrade is complete, data traffic is forwarded by the master switch. After the standby switch is upgraded, it becomes the master switch and starts to forward data traffic. Then the original master switch restarts with the new system software. After the upgrade is complete, the original master switch becomes the new standby switch in the stack.

Note:
Only the stack containing two member switches supports fast upgrade.
During a fast stack upgrade, to shorten traffic interruptions, ensure that upstream and downstream devices are dual-homed to stacked switches using Eth-Trunk.
To perform a fast stack upgrade, complete the following steps:
Load the new system software to the master switch.
Run the copy source-filename all#flash: command in the user view to copy the new system software to all the member switches.
Run the startup system-software system-file all command in the user view to specify the name of the system software to use at the next startup.
Run the stack upgrade fast command in the stack management view to start a fast upgrade.
After performing a fast upgrade, you can run the display stack upgrade status command to check the upgrade status.
That is all I want to share with you! Thank you!