Do you have Top-Of-Racks 6800IAs? I intend to upgrade my 6880-Xs in a couple weeks or so and I expect an outage since our 6800IAs will need to go through a reboot once the new update is pushed down from the host switch(s). So again, a system no downtime using "redundancy reload peer" may indeed work for the host pair but regardless if you have 6800IA attached, downtime is unavoidable. Anyone, correct em if I'm wrong...
OK, than you just have the chassis. I have 6800IAs connected to our chassis. They operate as FEXs, similar to NX-OS. From what I've researched and confirmed with TAC, they will indeed reboot once you push the update from the chassis to them. Thus, temporarily causing an outage since in our case, we have servers connected to them.
how was your upgrade ? Did you need to upgrade the firmware before the IOS or could you go from 15.2 to 15.5 with no problems?