Hello Blair, Copying the IOS file to all the switches in the stack is compulsory if the upgrade is performed via bundle mode. In install mode, the IOS file will be copied automatically from the Active Switch to all the remaining switches in the stack...

In INSTALL Mode, you only need to copy the IOS to the Active Switch of the Stack. The first step when you start the INSTALL Mode upgrade is for the Switch to automatically copy the IOS to the Standby and the Member Switches. See below : Switch# insta...

ISSU is definitely reliable, and it is indeed meant to perform software upgrades with ongoing production. It should be successful considering the pre-requisites, restrictions, and procedures are followed. In case of ISSU failure, we do have auto-abor...