Many people choose optical discs for backing up their most important files. DVD discs and Blu-ray discs offer the high capacity needed to archive information such as tax documents, family photos, home movies, as well as business documents and files. But which of these two types of discs offers the greatest longevity: DVDs or Blu-rays?
To answer that question, we need to look at three important characteristics of DVD and Blu-ray discs: how they are tested, the environmental conditions under which they are stored, and the hardware needed to play the discs back.
Major manufacturers of DVD-R discs occasionally make claims that their discs will last anywhere from 5 to 25 years once they are recorded. Keen observers will note that DVDs have not yet been around for 25 years, so how could media manufacturers possibly know that their discs will last that long? The answer is: they don't.
What media manufacturers do is test their discs using a process known as Accelerated Life Testing, or ALT. This process exposes the disc to extreme levels of heat and humidity that simulates years of storage. By testing discs for extended periods of 9 months or longer, engineers can mathematically calculate the failure rate based on their results.
Claims of disc lifespans are not an absolute guarantee of how long a disc will last. Rather, they are an indication of how well the discs performed in laboratory testing. A disc with a claimed lifespan of 25 years did better in testing (fewer failures) than a disc with a 5 year lifespan.
According to an article about optical discs on MonstersandCritics.com, Blu-ray discs have shown to last a minimum of 15 years in testing, with data retention of up to 30 years.
In a separate study conducted by TUV Rheinland, recordable BD-R discs were calculated to last up to 50 years after being stored at 80 degrees C and 80% relative humidity for 750 hours.
The hard coating found on blank Blu-ray discs offers superior protection against the elements when compared to DVD-R discs, which do not have the coating. In scientific tests, it appears that Blu-ray discs are the better format for longevity.
Of course, scientific testing can only estimate the lifespan of a disc under specific conditions. For most home and business users, the way the discs are handled and stored will greatly affect how long they will last. Proper care and handling of CD/DVD discs includes storing them safely in CD packaging such as DVD cases or CD jewel cases. Discs should also be kept in a temperature-controlled environment away from direct sunlight.
The conditions under which discs are stored vary from one user to another. The best quality disc will fail under extreme conditions, but a poor-quality disc might still be readable if stored properly. In terms of environment, neither disc format has a clear advantage.
So, we have seen that the longevity of Blu-ray discs appears greater in scientific testing, and that both formats are equally vulnerable to environmental conditions. One final thing to consider is the hardware needed to play a disc back. Blu-ray drives and players are backwards-compatible with DVD discs, but DVD drives are not forwards-compatible with Blu-ray media.
Although DVD may still be the most popular format of today, Blu-ray is growing quickly. If I had to guess whether Blu-ray drives or DVD drives would be more popular in the next two, five, or ten years, my money is on Blu-ray all the way.
With that, it is my opinion that recordable Blu-ray discs are a better choice for archiving important projects than DVD discs.