Although I will definitely carry backup for the time being, I certainly disagree with some of the above.
In the coming years, the internet will become as much a fact as power supply or water supply. Now you rely on your electricity supply for your set. I assume that you do not take a power generator every booking in case the power goes out.
In the case of the internet, you can easily bring this backup facility yourself by bringing a router with a SIM card. This allows you to use the wired internet connection of the location or event, as well as your own mobile connection. And then you also have your own phone as a hotspot as backup backup (could be a 3rd provider).
Then you can access your collection from multiple online sources (own files via different cloud partners, such as Google, Amazon, Dropbox … and on top streaming catalogs such as Tidal, Beatport etc …).