https://en.m.wikipedia.org/wiki/Bekenstein_bound
It gives the maximum amount of data in space before collapsing into a black hole.
It gives the maximum amount of data in space before collapsing into a black hole.
I find this useful in discussing solar power: there is an absolute maximum of 1300 watts per square meter; most people don't know this and implicitly assume substantially higher is achievable.
For the sorts of scales human beings are interested in, of course, the Bekenstein bound is a long long way from being relevant, and what matters for us in principle is volume rather than area. (There are practical difficulties in using "substantially" 3-dimensional regions for storage, but they have nothing to do with the danger of the storage device turning into a black hole.)