With the explosive growth in CD-R recorder and media sales comes a potentially dangerous situation of data loss due to incorrect selection of CD-R recorders, media, software, and procedures. A significantly increasing number of CD-R users are not only distributing information on CD-R media, they are now archiving information on CD-R media. Many of these users are archiving data unaware of several very important issues and limitations concerning CD-R technology.

The purpose of this document is to briefly expose CD-R technology users to important issues concerning CD-R technology and data archiving using a simple, practical checklist.

To assist CD-R users with the selection of CD-R technology and procedures, the following six-point checklist has been created:

• Check your CD-R media; is it suitable for Archiving?
• Are you using Optimum Power Control?
• Is verification after write ENABLED?
• Are you using a "Data Safe" disc labeling method?
• Are you creating duplicate discs?
• What are the costs if you lose data?

For many CD-R technology users, the contents of the above checklist may seem strange and unimportant. All six items listed above are very important, if not critical, when archiving with CD-R technology.

CD-R technology, especially CD-R media, is primarily designed for the data distribution applications. CD-R technology can also work well for many data archiving applications if the technology is properly understood and used.

There is one important difference between data distribution and data archiving. The data distribution market is driven by price. It is a large volume market and price is the only major deciding factor; i.e., quality and reliability are less important than price. On the other hand, in theory, the data archiving market is driven by preventing data loss and insuring that the archived data can be retrieved without error. Quality and reliability are the leading decision factors in this market, not price.

From a practical point of view, price does effect the data archiving market place. That is a major reason why CD-R technology is becoming so popular for data archiving applications. However the low price of CD-R technology comes with tradeoffs; including a reduction in quality and reliability when compared against other types of optical storage technologies; i.e., 5.25" optical technology.

Simply stated, with data distribution applications, the CD-R disc is replaced if it cannot be properly read. In the archiving market place, disc replacement may not be possible; i.e., a single CD-R disc has your one and only copy of the data.

The quality and reliability of CD-R media varies greatly. The CD-R media manufacturers are under tremendous pressure to manufacture very low cost media. In order to achieve these lower costs, manufacturers are developing and using many different types of materials and processes; including recording dyes and reflective materials. Some of these materials, i.e., recording dyes are well suited for the data distribution market place; however their suitability for the data archiving market place can be questionable.

Some helpful hints for selecting a CD-R media for archiving include:

1. A stable recording dye: I strongly recommend a true "Phthalocyanine dye" disc. This clear recording dye has a proven record of accomplishment in stability and longevity.

2. A reliable reflective material: I strongly recommend a disc that uses "Gold" as a reflective layer. Gold is an inert element. Its reflective properties will not change over time.

3. A protective top coating: Pick a CD-R disc that has a protective top coating. Most CD-R discs only have a lacquer coating on top of the reflective layer. These discs can be easily damaged. A few select disc manufacturers place an additional protective coating on top of lacquer coating. This additional coating can make the disc significantly more resistant to scratches, abrasions, peeling, and corrosive ink.

4. Media Compatibility: Ensure that the CD-R media meets, and if possible, exceeds all CD-R media specifications; as stated in the Orange Book. Some older and lower cost CD-R media will not operate with all CD/DVD devices. In particular, watch out for the speed rating of media; i.e., if the CD-R media is only rated for only 4x recording, do not use it at higher speeds.

5. A quality driven manufacturer: Pick a CD-R media manufacturer that actually makes the disc, makes it their primary business, and technically understands what the media can and cannot do. Given the very low prices of CD-R media today, you may be very surprised by the lack of knowledge of many manufacturers.

6. Lifetime warranties and accelerated aging tests: Warranties and aging tests are important, but the physical replacement of a faulty disc will not replace or recover your lost information. Watch out for marketing hype. There are no industry standards for accelerated aging tests.

Optimum power control is the ability of the CD-R recorder to optimally adjust the laser power to the CD-R media in order to produce the best possible writes. This is very important! Different media recording dyes, media reflective surfaces, recorders, and recording speeds, all significantly impact the quality of the write. This determines which CD/DVD devices can reliably read the written data.

For data archiving, always ensure that your CD-R recording system performs a "Running Optimum Power Control" when recording on a CD-R disc. This ability is dependent on both your CD-R recorder and CD-R premastering software. If you are not sure and you are archiving data on CD-R discs, ask your CD-R technology supplier/manufacturer.

When writing with a CD-R recorder, there is no automatic checking of the writes; i.e., a "write verify" command or "read after write". Thus, in theory, you could write an entire CD-R disc of bad data without any reported errors. Just because the CD-R premastering software reports that the disc write operation completed with no errors, it is not a guarantee that the newly recorded CD-R disc is free of errors.

Verification of the CD-R disc contents can only be achieved by reading all the data on the CD-R disc and comparing this data with the original image. Most software packages and duplicators have an option to perform this verification. When archiving data, it is strongly recommended that you enable it.

Most CD-R users give little thought to labeling their discs. This is very dangerous! There are several ways to label discs, and each method has its tradeoffs. In fact, some CD-R users that archive may tell you not to label the discs. In my opinion, this approach creates the bigger problem of identifying discs. Most importantly, if you are going to label your CD-R discs, use a method suitable for extended time periods.

Normal ways of labeling CD-R discs include: manually writing directly on the disc; applying an adhesive label to the disc; printing directly on the disc; and silk screening. When it comes to archiving data, here are the pros and cons:

1. Manual labeling of discs: OK for archiving if water based soft tipped pens are used. The use of solvent based pens, i.e., alcohol based permanent pens, can result in the ink eating through the top coating of the disc and damaging the reflective layer over a period of several months or longer; thus damaging the data stored on the disc. A hard tipped pen, i.e., a ball point pen, will most likely physically damage the surface of the disc; thus damaging the data stored on the disc.

2. Adhesive labels: I strongly DO NOT recommend the use of adhesive labels! First, the label over a long period of time will dry out and potentially start to bubble and peel. This can result in either: the disc getting jammed while loaded in a CD/DVD device, and/or the temptation to re-label the disc. If the disc gets jammed, it is very likely that the disc will be physically damaged. The removal and the re-application of adhesive labels are difficult and potentially destructive. When trying to remove an adhesive label there is the possibility of removing the reflective layer with the label; thus physically destroying the data.

3. Printing directly on the discs: This is OK for archiving. There are several manufacturers of CD-R disc printers, both ink jet and thermal. These printers only work with CD-R discs that have a special printable coating suitable for either type of printer. Please Note: Care needs to be taken in selecting a printable CD-R disc with a CD-R printer.

4. Silk Screening: OK for archiving if UV curable inks are used. Be sure the UV ink does not contain any chemically active components that can affect the disc after the curing process. Also, watch out for contamination of the recording surface by the silk screening process.

When archiving on CD-R media, I strongly recommend making at least one duplicate CD-R disc, then storing that CD-R disc in a jewel case and placing that jewel cased CD-R disc in an environmentally controlled dark room. Why the caution? First, the bare CD-R disc is physically sensitive to damage; i.e., scratches and contamination. A CD-R jewel case is an excellent low cost protective mechanism. Second, the CD-R organic recording dye is sensitive to selected wavelengths of light; i.e., UV light from the Sun. Prolonged exposure could potentially affect the recording dye and result in data corruption.

This is a situation that no one wants to experience, especially when archiving data. Rather than waiting for this to happen, it’s best to be proactive and plan for this event. If you think that it is not going to happen, think again! There is no perfect data archiving technology, including CD-R technology. Therefore, assess the direct and indirect costs of losing archived data prior to finalizing your data archiving application. The results of this exercise could cause you to rethink implementation and increase your initial investment!

Please Note: For those data archiving applications that can not experience a data loss, i.e., mission critical information, CD-R technology may not be the most ideal choice. Other optical storage technologies, i.e., 5.25" and 12" optical, can provide a significantly higher level of reliability, security, and performance.

There are numerous advantages to using CD-R technology for archiving. Unfortunately, CD-R technology may not perform as expected for archiving applications unless particular care is taken. I hope that this document will assist people in understanding the technology and aid in their success when archiving information on CD-R media.

As a professional in the optical storage industry for the past seventeen years, Graham Irving is a voice of experience and knowledge. Mr. Irving holds a B.Sc. in Computer Science from the University of Calgary, and has been a member of several boards and panels, including the American National Standards Organization Optical Disk Committee, X3B11 and X3B11.1.

Mr. Irving can be reached at:

INSTAR Corporation
Suite 306, 205 9th Ave. SE
Calgary, AB, Canada
T2G 0R3
Phone: 403-264-7274
Fax: 403-264-7286
Email: graham@instar.com