Secure Digital (SD) flash cards are not noted as a reliable place to store data for any length of time but that hasn't stopped storage giant SanDisk inventing a new type of SD card it claims can be used to keep images for up to a century.

As tempting as this sounds, it is unlikely that the average consumer will ever use the new SD WORM (write once read many) cards in its initial form. The capacity is currently fixed at a paltry 1GB, and as the technology's name suggests, WORM SD cards can only be written to once.  Not very practical for most people.

The new technology is in fact aimed squarely as high-specialised niches such as policing evidence gathering, where images must be stored in a tamper-resistant form without the risk of the data degrading over years or decades.

Digital imaging is not considered a reliable enough medium for such storage and today's police forces still widely use conventional 35mm film cameras to photograph crime scenes.

The 100-year data life claim is qualified by the company as “based on reliability data from internal, accelerated lifespan testing for cards stored at normal room temperature, with humidity and static protection.”  

Wider take-up of the technology will come at a cost, mainly because while any SD device can read the image files only those with an WORM-compatible SD card interface can actually record files. Such devices are thin on the ground and are unlikely ever to go much beyond the high-end digital SLR cameras the card is intended to be used with.

“SanDisk continues to work with leading makers of imaging, audio and video recording devices to implement SD WORM compatibility,” is as far as the makers will go right now.

While the SD card itself might last for 100 years it is a fair bet that SD cards will be an obsolete technology long before that point. Reading the card as an archive medium will mean having SD card readers to hand. At some point police forces will have to migrate the data to new equally resilient data reading systems yet to be invented.

The company hopes that the SD WORM system will find favour in other fields such as medical imaging, high-surveillance security, building compliance imaging, legal transaction recording, and possibly retail cash receipt storage. Wider acceptance would drive down costs.

What the SD WORM underlines is that the consumer industry has yet to be invent a reliable means of storing data such as images over a long period. We seem to be going backwards in fact. Mini-DV video tape is laughed at by the makers of camcorders and yet I'd bet my dollar on such a camera and tape outliving any of the fancier new SD-based cameras with their splurge of files.

Back up the data? Make sure it is encoded using the correct CODEC and back it up at least three times. Then remember where you put each copy.

It is still an extraordinary fact that digital technology is an incredibly unreliable place to store anything. It is the era in which everything is recorded to be pored over, but only fleetingly. The half life of data is a handful of years in some cases. This is a problem that needs to be solved even if almost nobody worries about it much yet.