Since I made the transition, I have kept all the cd's that I ripped to the notebook/ext hard drive; when I do a gig, I setup the cd players and analogue mixer, I also bring along the three cases of cd's which basically hold the music that is on the notebook. I run my laptop through that mixer's middle channel (2) just in case something goes wrong with the laptop I'm already set. Actually this has happened once, no one knew there was something wrong except me.
Hypothetically just in case Murphy decides to show his butt and cause something to malfunction.