It seems like optical discs (CD/DVD/BluRay) are the right idea, they're just not made from stable enough materials. As far as I know, you could apply the same t

It seems like optical discs (CD/DVD/BluRay) are the right idea, they're just not made from stable enough materials. As far as I know, you could apply the same technology used to make optical discs to a more stable material like gold. Assuming that you could get the same storage density as a DVD (which seems reasonable, given that we have the technology/know-how to make 25GB single-layer BluRay discs), you'd need something like 500-600 disks (if you etched both sides). I'm a bit suspicious of my math here, but if my back of the envelope calculation is right a single disc made of gold would be something like 0.8 kg. The nice thing about this solution is that there's a lot of existing knowledge about how to build and design optical media, how to build in parity checking, detect jitter when reading, etc. This could be relatively cheap to do in bulk also, if you found the right material (I just mentioned gold because I know it to be chemically stable, but there are probably better materials).