Project Silica extends storage reliability goals from “decades” to “centuries.”

Ars spoke Tuesday with Dr. Ant Rowstron, a principal researcher at Microsoft Research in Cambridge, UK, about an innovative cold storage project called Silica. Silica aims to replace both tape and optical archival discs as the media of choice for large-scale, (very) long duration cold storage. Microsoft Research is partnering with film giant Warner Bros., which is directly interested in reducing costs and increasing reliability in its own cold storage programs.

The medium in question is a block of high-purity glass, which has voxels etched into it with femtosecond lasers. Each voxel stores multiple bits in two properties, retardance and angle, which may in turn be read using microscope imaging and polarized light. Voxels may be written 100 or more layers deep in a 2mm-deep piece of glass, by focusing the laser to the desired depth within the block itself.

The speed of both reads and writes to Silica currently leave something to be desired—it took approximately a week to etch Superman ‘s roughly 76GB of data last year, and Rowstron estimates it would take about three days to re-read the data, with advances made since. The technology is still in its infancy, of course, and large decreases in time required for both writing and reading are expected moving forward. Rowstron says he still doesn’t expect anyone is likely to try to actually play Superman directly from its Silica record—but that’s not what it’s intended for.

True long-term archival of data is a very expensive proposition. When I was in college, I took part in a research project for my university’s archival department—the department needed a database application to index and track its digital media collections, in large part so that it would be able to budget for and carry out archive renewal operations within expected refresh cycles. Its older analog audio and video tape recordings needed to be digitized, and its optical CD and DVD recordings needed to be read, checked for integrity, and burned onto new media before the original discs delaminated.

This archival refresh cycle rapidly becomes daunting at any significant scale. If you assume a collection of 10,000 CDs and a team of three or four undergrads with CD-RW drives and a huge stack of discs, you’re looking at more than a year of full-time work to refresh them. (Warner Bros., which has a rather higher budget than the rare collections department at my alma mater’s library, migrates its own digital archival data on a strict three-year cycle.)

Making matters worse, the lifespan of burned CDs is frequently very short—they can easily begin failing after only five years, so they should at the very least be tested that often, if not refreshed “whether they need it or not.” It is possible to extend optical discs’ lifetime significantly by storing them at 5C/41F and 30% relative humidity, but this adds a significant extra expense to storage and maintenance.

This is the problem Project Silica is poised to solve. Although it’s currently fairly slow to read or write, Silica’s medium—no more or less than high-purity glass—shares none of tape, optical disc, or even paper’s failure modes. A Project Silica glass block is not a compound medium; there’s no plastic outer covering to wear off as there is with CD, DVD or Blu-Ray, and there’s no magnetic medium to physically lose from the surface of a tape or hard disk.

Silica is expected to survive for thousands of years in nearly any temperature, humidity, and chemical environment—it’s literally just glass, and the physical and chemical properties of glass are extremely well understood. We can only guess at the properties of more complex manufactured materials (tape, disk, and so forth) using accelerated aging techniques, but glass artifacts thousands of years old are readily available for study.

• This is the heart of Project Silica—the laser and lensing equipment that burns the data into the medium. Microsoft scientist James Clegg is seen here loading a glass sheet into the machine. Jonathan Banks / Microsoft
• Sometimes, “science” can mean “boiling your data alive.” The team has baked, boiled, microwaved, degaussed, and scoured its glass with steel wool without losing the data stored inside. Jonathan Banks / Microsoft
• This cone beaker, part of the Cornell Museum of Glass’s collection, dates to roughly 400-600 CE. Unfortunately, the Anglo-Saxons weren’t much into lasers then. Cornell Museum of Glass