Some years ago the historian Gerhard Weinberg published an article (which I can't seem to lay my hands on right now) arguing that the best way to preserve records, against the possibility of some kind of apocalyptic disaster, was microform (microfilm, microfiche).

He was concerned about the rising amount of data that's stored only in electronic formats, and the rapid obsolescence of electronic storage media -- for example, how are you going to read an 8 inch floppy disk in the year 2100?

His argument was that microform data is physically more durable than paper, and takes up less space, and even after an unimaginable disaster in which the planet goes back to medieval or earlier technology, it wouldn't be too long before somebody would invent a magifying lens, which is all you need to read microform. It'd be a bit longer before somebody invented a 1950s-style computer tape reader.