[zmmmmm]

In our case, it's effectively "forever" storage. Which is to say, we are obliged to retain data for at least 10 years but targeting 20 years.

At this point we are doing this with on-premise tape backup but that is in part because I'm yet to be convinced that we can trust cloud providers with this, especially since our future retrieval needs are unclear (some outlier scenarios could see us needing to retrieve substantial fractions of the data). Not to mention that even the coldest cloud storage seems to still be substantially more expensive than DIY tape archival (admittedly, not taking into account things like internal IT staff costs etc).