Ask Slashdot: Best Medium For Personal Archive?

An anonymous reader writes What would be the best media to store a backup of important files in a lockbox? Like a lot of people we have a lot of important information on our computers, and have a lot of files that we don't want backed up in the cloud, but want to preserve. Everything from our personally ripped media, family pictures, important documents, etc.. We are considering BluRay, HDD, and SSD but wanted to ask the Slashdot community what they would do. So, in 2015, what technology (or technologies!) would you employ to best ensure your data's long-term survival? Where would you put that lockbox?