Posted in: Solutions, Special Report, Storage
When DVDs came on the market in the mid-1990s, it wasn’t just the movie fans that were happy — IT pros thought they’d been given a great data storage medium. But are DVDs really suitable for storing information long-term?
For data managers, the existence of a standard, portable medium for archiving data was very welcome indeed. DVD was seen as safer than tapes and magnetic drives, and more universal than older optical disks. Manufacturers claimed lives of 30 to 100 years for their DVDs, certainly more permanent than anything else around. Over the past decade, millions of files were placed for safe-keeping on DVDs.
But DVDs suffer from a phenomenon called bit rot (also called bit decay, data rot, or data decay). Bit rot happens when the single bits of data get wiped out or modified. This always existed on electricity-based magnetic media, which is why programs sometimes “went bad” on hard or floppy disks. But DVDs (and CDs) have similar problems. Unlike magnetic disks, writeable DVDs store bits using a set of dyes under the surface, dyes that are “imprinted” using a laser to turn on and off specific bits.
The rate of decay can be influenced strongly by storage conditions. Humidity, temperature, light and handling can cause changes in the dyes, and therefore, DVD archives should be stored in a dark, cool, low-humidity environment with minimal handling. That’s still not the practice at many companies.
But even with the greatest care (and the best gold-plated archival DVDs), bit rot does happen. After all, it can only take a few altered bits to change a critical number or for a critical link to get altered.
The problem is that DVD technology dyes are vulnerable to a wide range of environmental changes. And what about Blu-Ray? Apparently it’s even more vulnerable, as its dyes are even closer to the surface.
Need proof? The U.S. National Archives (people who we assume know something about storing data) says: “CD/DVD experiential life expectancy is 2 to 5 years even though published life expectancies are often cited as 10 years, 25 years, or longer.”
This means that if you use DVD, you should make several backup copies, and you need to test them regularly and re-burn DVDs every few years. It’s in no way a permanent or even long-term archiving solution.
One solution you might check out comes from a new startup called Millenniata.
Millenniata writes on DVD-size media using an altered DVD writer with enhanced lasers. Instead of altering dyes, it actually writes tiny pits into the discs, below the surface. These pits are unalterable under any normal condition. The company even shows off in a video by plunging the written media into liquid nitrogen, then boiling it, then reading it good as new. (Don’t try this with your regular DVDs.)
While it requires special disc media and a special drive to write them with, these disks can be read using most desktop DVD drives (the company notes that they have found some really cheap drives that don’t work very well). The “etched” bits look like regular dye bits to the reading system of standard DVD drives.
The company, which has been working with Sharp Electronics, is starting to ramp up its marketing efforts and finish testing with some major archivers (governmental and corporate). It’s also undergoing more rigorous third-party stress tests.
The list price of the disc writer is $2,500 and the list price of discs will be $15. Not cheap, but think of the cost of testing and re-burning hundreds of DVDs or the even bigger cost of losing critical data. Keep an eye on this company –- if their claims get borne out, this will revolutionize the data storage industry.