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DVD Durability

When you entrust your backup data to recordable DVDs (DVD-R, DVD-RW, DVD+R, or DVD+RW), it's certainly reasonable to wonder just how long you can expect the DVD to hold the data accurately without degradation. You don't want to pull out a DVD backup of a tax return or family photos in seven years, only to find that the disc has become unreadable.

Can You Trust Manufacturer Claims?

You may see claims that recordable DVDs will last decades, or even 100 years. Of course, recordable DVDs have not been around for 100 years, so how can anyone claim to know they will last that long? The answer is that manufacturers subject their test DVDs to certain kinds of stress and then extrapolate from those measurements to guess how long the data will last.

Heating and cooling a disc repeatedly under humid conditions to estimate media lifetime is certainly better than no testing at all. However, it's unlikely to be highly accurate, and cannot take into account any threats to the media that were not tested for. For example, it was discovered not so long ago that some areas of the tropics

Making Your Recordable DVD Last

Those optimistic manufacturer claims contain some optimistic assumptions that you can use to improve the likely lifetime of your own DVD data storage.

First, consider how you physically store your discs. Those 100-year estimates assume you have a room whose temperature is never more than 2 degrees off from 25 degrees Centigrade, and that you can also always keep the relative humidity very close to 55%. They also assume there is no UV radiation around and no corrosive gas in the air. Are your DVDs stored in a sunlit room that swelters in the summer and is occupied by a heavy smoker? Then don't blame the manufacturer when your DVD-R craps out much sooner than 100 years.

Second, consider how you handle the recordable DVD discs. The manufacturer assumes you will never touch the recording surface and never inflict scratches on it. Writing on the non-recording side with the wrong kind of marker, or putting a label on the DVD that contains chemicals that can seep into disc are also things the manufacturer assumes you will never do. If you walk through an office and inspect some DVD media from several different people, you'll probably find that these are highly optimistic assumptions.

Finally, consider how much you paid for your recordable DVD. You can safely assume that the very cheapest recordable DVDs use technology and quality control that is least likely produce the most durable discs.

Conclusion

The bottom line is that DVD durability can be quite good, but can never be counted on. Store your recordable DVDs vertically, protected from sunlight, in a room that avoids wide variability in temperature and humidity. Do not label the actual surface or write on it if you can avoid it (if you do write on it, write on the inner hub where there is no data, and use a pen specifically sold for writing on CDs or DVDs).

With proper care, your recordable DVDs should easily be able to last a decade. However, there is absolutely no way to guarantee that an individual disc does not have a defect that will cause it to fail earlier. Thus, as with all backup media, the safest course is to always have crucial data stored in more than one place, and have a regular program for checking the data integrity of your backups.


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