Building the million year disk

We store enormous amounts of data today and that is generally a good thing. The problem: we store on disk drives that may last five or six years and may be economic for three.

That is not even a medium-term solution. So researchers have been searching for more.

Whatever intelligent beings follow us may have some interest in the nature of our culture.  This is the goal of the Human Document Project.

Researchers at Hitachi Data Systems recently demonstrated quartz storage, readable by optical microscopes, with an expected life of millions of years. But there is a new entrant in the race for long live storage.

Researchers investigated a tungsten disk encapsulating silicon nitride which should last at least 1 million years. This dwarfs even the 1,000 year DVD.

Why bother?
Homo Sapiens is only a few hundred thousand years old. We may not make it to 1 million years before we either destroy ourselves or evolve into another species. Whoever or whatever intelligent beings follow us may have some interest in the nature of our culture.

This is the goal of the Human Document Project.

The problem
All data is volatile, which means it is not possible to store it forever. Even quartz will eventually wear away.

A long-lasting medium requires a high energy barrier against erasure. Strong thermal stability is key. Researchers found that the required testing temperature to show the data is stable for a million years is 380° Kelvin - a little higher than the boiling point of water.

This led to the choice of tungsten with embedded silicon nitride - transparent to electron beams - as the medium of choice. Tungsten has a high melting point and low thermal expansion. Silicon nitride has a high fracture toughness and a similar thermal expansion.

A related alternative is a medium with high reflection contrast. This is enables much thicker and tougher base since the medium doesn't need to be transparent. The two are similar except for a silicon baseplate:

They propose to write the data using barcodes and QR codes. QR codes can lose up to 7% of the data before becoming unreadable.

Using small QR codes it would be possible to use an optical microscope to read the disk. Embedding even smaller QR codes within each of the larger QR code pixels would dramatically expand the information capacity of the storage.

But the highest storage density would be achieved with electron beam readable media where the embedded silicon nitrite would form the zeros and ones of the code. But this would mean a much thinner and more fragile disk.

When tested the media was able to survive temperatures up to 713° Kelvin which suggests that with further research a true 1 million year disc is possible.

The Storage Bits take.
This is advanced research, not product development. But it points the way to a much more robust long-term digital storage.

Our entire digital civilization rest on persistent digital storage which requires frequent replacement to preserve data. As long as storage densities are increasing this is not a big problem but anything that cannot go on forever won't. And when that happens we will have tough choices to make about what data gets preserved and what doesn't.

If a variation on this technology can be commercialized we may be able to save a lot of energy as well as much of the fabric of our digital civilization. That would be a Very Good Thing.

You can read the paper Towards Gigayear Storage Using a Silicon-Nitride/Tungsten Based Medium by Jeroen de Vries, Dimitri Schellenberg, Leon Abelmann, Andreas Manz and Miko Elwenspoek here (pdf).

Comments welcome, as always. What do you think should be preserved for 1 million years? Miley Cyrus or Beethoven? Or?