Pretty sure it's going to vary from person to person, but I have a LOT of digital media, mostly from my photography and videography, and to me archiving is still online, just on the big slow NAS (relatively speaking, it's actually pretty snappy) instead of the fast DAS, whereas "backed" up is a cold, offline storage medium, one copy of which is held off-site. The latter for me are external USB3 HDDs which get replaced every few years, because that's still cheaper than tape, faster than tape, and ensures that I have to re-verify (and occassionally prune) the data when I move it to a new set of drives (I have a few extra steps in the process to avoid fat-finger problems and so on than just copying the data over, and so far haven't lost a single file).