I have experience with a similar setup with EX4550's.
The bad news is that, indeed, you can't do it without any interruption
and indeed you need to have the same FW version on both units.
The good news is that in most cases you can do an "ISSU" (in service
software upgrade) where the complete process is performed in such a way
that never more than one unit is offline.
If you have everything connected in a redundant way, this should allow
you to do an upgrade without downtime.
Original Message:
Sent: 4/6/2023 1:28:00 PM
From: dtopojr
Subject: Upgrade core Virtual Chassis without disruption EX4600
Hello all... I'm just curious to pick some brains here and see what you think the best method is to upgrade a pair (virtual chassis) of EX4600s. This VC stack serves as our campus core- hence, if I'm able to upgrade JunOS while keeping operational connectivity throughout the process (reboot and such), I'd love to hear how. Since both units need to be running the same JunOS version to facilitate the VC, I don't see any way to NOT have this be disruptive.
These core switches carry all our ethernet traffic as well as SAN traffic- so keeping them up is in our best interest. Otherwise I suppose I will need to shut down all our VMS that live on the shared SAN storage - upgrade, reboot the switches- then bring back our vcenter\vms etc.
Appreciate any input ! Thanks ...Dennis