April 27, 2003

Long Term Backups

Dan Hon finds a Slashdot comment giving sage and time-tested advice on the appropriate long-term data backup strategy. If it's good enough for Ashurbanipal, "King of the World, King of Assyria!" it should be good enough for you:

Slashdot: Etched stone seems to have a staying power of approximately 10,000 years, even with some outdoor exposure.

Earthenware tablets, made of clay fired at low temperatures (1816F/991C), seem to do nearly as well, while stoneware tablets, made of clay fired at high temperature (2345F/1284C), last about the same as actual stone. Ceramics have relatively high resistance to moisture and thermal variation. Depending on the clay composition and the application of glazes, there is variable resistance to acid. Ceramics do not handle physical shock particularly well.

Glass can last thousands of years, but is vulnerable to shattering or acid.

None of these, however, are earthquake-resistant. Outside of the immediate blast radius, they're good against nukes.

Etching into stainless steel is good, although in the event of a nuclear attack, this would be succeptible to melting (or self-destruction due to induced current) within a certain area. It handles thermal and moisture extremes pretty well, but doesn't handle acids well.

Stamping into gold foil is expensive, but quite durable. It's immune to some of the chemical risks posed by steel, but is more likely to be stolen. It's also not as hard, thus leading to risk of data corruption or loss via impact.

Parchment, preserved lamb or sheep skin, can last a very long time (on the order of 2,000 years) in the right conditions. It does well with exposure to electromagnetic radiation, but deals badly with moisture or excessive dryness, and is highly vulnerable to acid.

Delay-line broadcast (reflecting your data with a laser off of a distant object, and rebroadcasting ad infinitum) is fairly reliable until occlusion of the data path occurs, or the transceiver is smashed, unplugged, EMPed.

Yeah, data preservation is hard in the long haul.

Posted by DeLong at April 27, 2003 10:28 PM | TrackBack


Sadly, or not, as an architectural historian, I can tell you one really bad thing about relieving a message into dressed stone: future generations tend to look on the cut stone used in a prior generation as building materials just begging to be recycled into a new use. By the 16th Century, when Rome's urban poplulation had dropped to something like 17,000 people and farmers were growing crops inside the old city walls, most of the city's monuments were regarded as quarries. Same is true for many Greek monuments, as for the stone that sheathed the pyramids of Egypt.

Of course, even the reused stuff can retain the message scrawled on it, to be found centuries later when the second (or third) building it's been used to shore up falls over.

Posted by: Brian C.B. on April 28, 2003 09:52 AM

To my mind the more fascinating problem is decoding our backups. Without a Rosetta Stone to span languages, how do we read the data we've preserved? Must every data storage medium have the equivalent of the Voyager plaque?

There's a far more critical problem than media longevity today. Technology is not hanging around long enough for us to trust any media for long. When's the last time you saw a 8" floppy drive? Or quarter-inch tape (to say nothing of nine track)? I am willing to bet that the majority of digital records encoded in the seventies and early eighties can't be ready outside of specialist retrieval firms. Will the CD or DVD disks last any longer?

I am a firm believer that only the surreal explains everything. This situation rteminds me of nothing so much as the plague of amnesia in One Hundred Years of Solitude.

Posted by: Jon Gallagher on April 28, 2003 03:02 PM

A potential problem with gold foil is that it can be worn as jewelery. This might be a spy's dream come true. Who needs a drop box, untracable IP or disc when gold foil can be paraded safely at the White House or Pentagon? It could make for an interesting and glamerous movie.

Posted by: vachon on April 28, 2003 05:32 PM

News Flash: The Library of Congress is re-recording music to a more stable and long lasting format: acetate 78 RPM discs, with 2-3 min. of recording time on each side. No word yet from Arty Shaw or the Fletcher Henderson estate about left over stocks of old Victrolas capable of playing said 'records'.

Posted by: VJ on April 28, 2003 11:49 PM

Sort of an interesting aside on the Roestta comment, there is a project for written languages at http://www.rosettaproject.org/.

As far as data storage formats, I think we're doing better with the current generation of storage (DVD & CD). The important consideration for these is that they are commonplace (ie, in many homes), whereas previous data storage devices were comparatively rare.

It is also a good idea, I think, to continue the trend started by the follow-up of CD by DVD...keep the same form factor, and make the devices backwards compatible. This, of course, only addresses the immediate future. I don't have a lot of ideas for longer than that, especially if lack of electricty is a constraint...just print a lot of books of important information, and hope some survive, I guess.

Also sort of ontopic, but this link is along the same lines:"

I had to link the Google cache, as the original seems to be messed up right now.

Posted by: AC on April 29, 2003 03:29 PM

This is really a fascinating subject, and Greg Benford wrote an interesting, if somewhat axe-grinding book which explored, for instance, all the considerations involved in making a nuclear waste site unattractive to future human visitors. Not quite the same problem, but a similar one, since part of it involves making a message last for centuries.

As someone with a lot of experience in film, I can tell you, there's no substitute for simply saving things in as many places as possible. Start putting your home movies on DVD now, and send copies to relatives in other cities... and be prepared to get them off of DVD and onto something else in about 10 years.

As for everything really important to human civilization, next time we go to the moon, we should leave a copy there.

Posted by: Mike G on May 1, 2003 09:03 PM
Post a comment