Backup Data on CD/DVD:

Safe Choice or making coasters?

Backing up data has often been a problem for many companies. When you look at the methods that are used, people often used tape, but with the advent of inexpensive CD and DVD burners, many people are looking to the portability and ease of backup to these small silvery disks. But have you checked the expiration dates on that media, are you making backups you can read, or just coasters? Let me explain.

Digital Data Fade
Many people backup their data on CD media and now the move to DVD media for storage has started. You select your files and burn them to a disk; safe, secure, easy to store and reliable. Well maybe not that reliable. The problem with CD and DVD technology is that no matter how good your burning device is the media and its contents are subject to Digital Data Fade. What is Digital Data Fade? Well, there is a difference between the CD’s that come mass produced from a factory and those you can buy and burn data to yourself. The burnable disks, be they CD-R, DVD+R or DVD-R all use a type of technology that allows the laser beam focused from your drive to burn a hole through a layer of ink in the media. The resulting holes and spaces are then read as 1’s and 0’s when reading the disc. Just as with digital tape and audio tape, there is a difference in the quality of these disks.

Magnetic Tape History
When magnetic tape entered the scene, data, all kinds, was able to be stored on the medium. The substrate or carrier for the tape was typically nylon, Mylar or some polymer base. Bonded to that base was rust. Yes, rust. The size of those particles of rust and the material used to bond them to the tape resulted in the quality of the recording and its shelf life or expiration date. An electromagnet was passed over the rust particles and they were magnetically charged. Those charges were then read back as music, computer programs or data. Technology was little different for floppy disks. Coercivity is the ability of magnetic media to hold the charges applied to them.  The higher the coercivity, the better the media retain the information and with what quality. It is measured in Oersteds. Anyone who ever recorded a cassette tape knows what I am talking about. The tapes you get cheap in a poly bag were ok for speaking but for music, you needed something better. Over time, they all degraded, making the music sound muddy or in the case of floppy disks, read errors or CRC errors were the norm.

Enter CD’s / DVD’s
Remember when CD’s were introduced for audio? We were told they would last forever and were virtually indestructible; yea about as indestructible as those ‘unbreakable’ vinyl records! The fact is they were subject to scratching, and those were the factory discs. When burnable media arrived on the scene, they were subject to scratches too, but also to other problems based on the technology that burned the disc itself. But just as with magnetic media, quality enters the picture. Some burnable disc media, unlike factory discs, do not have a top and bottom layer of polycarbonate, but are simply shellacked on the surface. Another variable is the type of ink used in the media and how small an area is actually ‘pitted’ when burned. Beyond that, some media continues to degrade in the area it has been burned and over time this results in read errors and CRC errors, the same things that plagued magnetic media.

How Safe Is My Data?
Unfortunately, not that safe. The permanence of the burned image on CD-R’s / DVD-R’s is not all that permanent. Contrary to popular belief, most CD-R’s / DVD-R’s are not permanent at all and low priced CD-R’s / DVD-R’s may not be readable, at all, and error in as little as two years. Come on, show of hands, anyone had a disc that was fine go bad? Hands down. While inexpensive CD- R’s / DVD-R’s media is great for moving files from one PC to another it is risky if you are using it to archive data or any kind. Quality, name brand CD-R’s / DVD-R’s utilize high quality recording and reflective layers and are well sealed to reduce the harmful effects of our world. The material used for the substrate in CD-R’s and DVD’s is polycarbonate. It must be impermeable to gas (oxygen). Most plastics are not, but some plastics are better than others.

Even more important is the quality and thickness of the top coatings used to seal layers coated on the substrate. Factory CD-R’s / DVD-R’s are made by “stamping” the information into the plastic substrate. Then an aluminum alloy coating is applied to the “bumpy” stamped surface, thus allowing either the laser to reflect off of this reflective layer and a “1 bit” is determined, or the laser is deflected by the “stamped” bump and a “0” bit is determined. The recorded layer of a CD-R/DVD-R is not “sandwiched” within the plastic substrate but rather a clean lacquer protective layer is put on top of the aluminum reflective layer and the label is put on top or a thick ink coating applied. As the CD-R/DVD-R is read from the plastic side, a paper, plastic or ink label applied to the CD provides extra protection against the data surfaces being scratched. Because CD-R’s and DVD-R’s are not stamped with data; they are burned with data by the end user. The plastic polycarbonate is stamped with splines (tracks or lines) for the laser to follow. The recording layer is also referred to as the dye layer and it is sprayed on top of these splines. Four basic chemical formulas are used for the recording layer dye:

1.Cyanine / light green/blue in color, costs less to make, most common and lowest permanence
2.Phthalocyanine / transparent with a slight green tint, Highest permanence and second most common
3.Metallize Azo / blue, Similar in quality to Phthalocyanine, costs less to make and are not common
4.Formazan / light green, combination of Cyanine and Phthalocyanine, similar in quality to Phthalocyanine, costs less to make and are not as common


Data or Coasters
The choice of data or coasters is really up to you. How so? Well, it comes down to what kind of media you are using. Generic media is just that-- generic. It is less expensive to purchase but can actually cost more in the long run in the loss of data, man hours and possibly even business. Generic media does not have any ‘shelf’ life. It is what it is, generic. Archival media does have a shelf life and therefore is not subject to an expiration date. The current standard for archival optical media guarantees that the information on the disc can be read for 100 years. Now, I often wonder how they come up with that figure, but it stands to reason if one product has a guarantee of a 100 year data readability life while the other has no life rating at all you need to take two things into consideration; first that one of these kinds of media is of a higher quality and two that one is cheaper than the other. Generally speaking, when you go cheap, you get exactly what you pay for. We in the industry as a Value Added Reseller (VAR) have been saying that for years, but this is just another example of that

How Can I Get Archival Media?
You can get archival media by simply asking for it. In most cases even the electronics superstores will have it. Most major name brands have archival media available. If the brand name is not one you have heard of or if the price is very cheap, you are probably looking at a generic disc. You can also select media from sources that are know for their shelf life readings, i.e. Taiyo Yuden, Verbatim, etc.. Their DVD media has a less than 0.006% failure rate, a 100 Year Durability Data Integrity Guarantee and the Lowest Jitter and Deviation Levels in the Industry. Their CD-R media is known for being the highest quality and most reliable CD-Rs available, outperforming the competition in recording accuracy in a wide variety of data and audio applications

How can I get more information on this subject?
If you have support with us, ask us. Often times we will have additional suggestions you should think about in the long term when dealing with backup technologies and media choices. If you have questions or comments about this article, contact me (JohnBoline@hagerman.com).


 

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