Better Burning: 5 Tips for Safeguarding Your Data

Ever worry about whether your newly burned disc will be readable years from now? Here's how get the most from your optical media.

Melissa J. Perenson, PC World

Have a question or comment? Drop a line to Melissa J. Perenson.

We burn discs so casually, taking just minutes to copy data to CD or DVD. But copying data to optical media is actually a complex process dependent on both the quality of the drive and the quality of the media. A problem with either could affect the quality of the disc--and the integrity of your data.

The fear of an optical disc failing is right up there with hard drive crashes as a recurring source of angst. And rightly so: If a disc has problems, your irreplaceable data may be unreadable the next time you plop the disc in the drive. Scores of wedding photos, the family reunion for Grandma's 90th birthday, your start-up's critical business plans and financials--all could disappear with the passage of time.

Unfortunately, there isn't one single foolproof way to guarantee your data will be safe.

It's easy to recommend that you stick with high-quality media, but harder to avoid the pitfalls. Even if you avoid the cheap generic media that's available in bulk, it's next to impossible to isolate the best of the rest. Variables contributing to media quality are seemingly endless, as Fred Byers of the National Institute of Standards and Technologies noted in one of my earlier columns, "When Good Discs Go Bad." Dedicated media testers know how difficult and complex the process of finding the best media can be--and they typically use equipment that costs thousands and thousands of dollars to do this.

I don't have such equipment at my disposal--and chances are, neither do you. But although we might not be able to perform extensive tests to identify the best media, there are steps we can take to minimize the chances that the discs we use become unreadable one year or ten years from now.

1. Make Sure You Got It Right

You need to verify your data. The process is tedious and time consuming, and yet this simple step is the first line of defense in ensuring your data's safety. Most burning software packages--including Ahead Software's Nero 6 Ultra Edition and Roxio's Easy Media Creator 7--support data verification, a process by which after a burn, the software does a bit-by-bit comparison of the data you just copied with the original data still on your hard drive. Says Robert DeMoulin, product manager at Sony Electronics: "If you do the verification after the burn--and that verification is successful--then this is your best safeguard, and the single best thing you can do."

Even if the disc plays fine, and the data verification goes smoothly, I recommend checking the disc for errors. Not all CD and DVD burners are capable of reporting error information; this depends upon the drive's chip set. However, many drives support this feature--including models from such major vendors as Lite-On and Plextor.

By design, CDs and DVDs have error correction capabilities built in that provide redundancies on the disc to compensate for problems as they arise. Error correction is a function of both the drive reading the disc and the disc itself, which is one reason that one drive might be able to read a disc that another drive can't.

Nero CD-DVD Speed (included in Nero 6), InfinaDyne Software's CD/DVD Diagnostic, K-Probe (a downloadable app for Lite-On drives), and other similar utilities can report on disc errors and provide valuable baseline information about the quality of the burn you've produced. The idea here isn't to expect a disc with absolutely no errors. In fact, says Paul Crowley, chair and founder of InfinaDyne Software, "expecting 0 errors is unrealistic." You will always see some C1 errors, the lowest level of errors found on a CD or DVD; both the drive and the media's error correction code can easily and seamlessly compensate for these errors. But, Crowley adds, the number of errors you'll get will depend on the drive and the media being used in combination with one another.

As time passes, and dust, fingerprints, scratches, and particulate debris affect the disc during use, you're going to further tax the disc's error correction capabilities. "Those scratches can cause errors," says Memorex's technical communications manager, Terry O'Kelly. And although "most of those can be forgiven, the basket can only hold so much." One more scratch or seemingly invisible nick could pass the threshold of what error correction can handle. Once that happens, you're left with an unreadable disc.

The idea, then, is to minimize the errors on a disc from the outset, thereby improving the odds that error correction will be able to cope as the disc degrades over time. "If the error rates are very low to begin with, that gives you a better safety buffer," says O'Kelly.

2. Pay Attention to Error Reports

Ahead's Nero CD-DVD Speed can test for C1 and C2 errors.

Programs like CD/DVD Diagnostic, K-Probe, and Nero CD-DVD Speed serve up fancy, geeky charts showing the number of errors you have on a disc. These charts, if interpreted properly, can help you determine whether a disc has more errors on it than it should. For example, Nero reports on the C1 and C2 errors on optical media, and does so with error correction enabled. CD/DVD Diagnostic disables error correction as much as possible so it can provide the closest approximation to determining whether the disc can be read by a different drive.

"We see two classes of errors--those that the drive did recover from, and then those that the drive couldn't recover from," says Crowley. "Both of these errors can come from things that interrupted the write laser on the surface of the disc--like dust and fingerprints--or from failures in the media, pinholes in the dye, things like that. If you have errors on the disc because of any of these, the disc is only going to degrade from there. You're starting off with problems. Eventually, you're going to see the recoverable errors increase to the point where they're no longer recoverable. Once you cross that line, you have a spot on the disc that cannot be read. And when you reach that point, you're in trouble. You want to prevent the wear from getting to that point."

Disc error reporting is complex and technical. Explains Memorex's O'Kelly: "C1 errors are small, random errors easily handled by the [disc and the drive's] error-correction codes. If the errors are larger in size or in frequency, they become C2 errors handled by the C2 decoder. Block error rate, or BLER, is the number of data blocks that have C1 errors in them. The Red Book specification [the official CD standards] requires fewer than 220 [errors] per second, averaged over a 10-second time span. The technology gets even more complicated as you delve deeper."

Even the experts disagree on how many errors are tolerable. Says Craig Campbell, technical support manager at Ahead Software: "You don't want to see any C2 errors at all. If you do see C2 errors, it could be because of scratches, poor media, or dust. It could be a problem with the burner, or that the media is not supported at that speed, or a problem with the media."

The bottom line: Use the software to predict potential trouble, but remember that there are no hard and fast numbers to go by. And errors can be caused by something as simple as a dusty disc.

3. Test Your Media

While error-checking software can certainly help you learn something about a disc you've burned, the accuracy of the results can vary from drive to drive. And just because the software reports a disc full of errors, don't assume the media itself is at fault. Says O'Kelly, "It could be there's nothing wrong with the disc, and nothing wrong with the drive; they're just incompatible with one another."

Which is why you should always test your media with your drive. "Find the best media for your burner by burning discs and seeing which has the lowest error rate," suggests DeMoulin. "Some brands are kind of finicky."

Though finicky may not be a technical term, it accurately describes the situation. In theory, any disc should work with any drive; after all, the drives and the media both conform to basic manufacturing standards for the various disc formats. In reality, the drive's firmware is coded to match the media's identifying stamp; and if support for a specific media type isn't in the drive's firmware, the drive may not perform at its best. For example, it may not achieve its maximum write speed; or, as O'Kelly points out, it may burn a disc full of errors.

Most brand-name drive manufacturers post a list of compatible media on their Web site's support pages, and most offer firmware updates to keep their drives current as newer media is released. (See my column on firmware upgrades for more information.)

4. Choose the Right Media

Ahead's Nero CD-DVD Speed can provide specific information about the disc you're using, including the manufacturer and the precise capacity.

I recommend buying a handful of different types of media and giving each of them a try. Use the Nero or CD/DVD Diagnostic utilities to determine the media's origin and type. (You can find ten different brands on a store shelf, and all of them could originate from the same manufacturer and production line.) Then burn some test discs, and compare the results. This method lets you isolate the best media for your drive before you start archiving your important data. And while you're experimenting, I suggest trying to burn at slower or faster speeds.

The idea of burning at slower speeds originated a few years back, with the second and third generations of CD burners. Sony's DeMoulin recalls that the standard for disc mastering used to be 1X. "It used to be that a slower speed gave you the better burn. But with today's faster drives, sometimes the middle speed is the best." Some drives, he adds, start at 8X for a CD-R burn, so you can't turn the speed down any further, even if you wanted to.

Chris Bailey, media product manager at TDK, says there is a correlation between high-speed burns and the number of errors incurred during the burn. "The error rate is much higher on higher speed CD and DVD drives, and the function of errors is related to the media and the burner combined," Bailey says. "The higher speed makes it more difficult for the burner to read the media. And then, of course, media quality is a factor, too."

But slowing down the burn speed is not a panacea for disc error woes. Some experts, including InfinaDyne's Crowley, point out that there hasn't been conclusive evidence that downgrading the speed from the drive's optimized speed may be helpful in achieving a better burn. Others, including Memorex's O'Kelly, indicate that varying the disc's write speed can help improve the burn. Often, slowing the drive down means it doesn't vibrate as much.

Determining what combination of speed and media is best for your drive requires some trial and error. "Sometimes slower speed works better; sometimes faster speed works better. It depends upon the sensitivity of the dye on the disc, to a degree," O'Kelly says.

5. Handle With Care

Regardless of all the foregoing, here's one simple maxim for making your CDs and DVDs last: Handle your discs carefully. Dust, fingerprints, and other contaminants can damage discs easily. So, too, can heat and ultraviolet light. So take care when you store your discs: Keep them in their jewel cases and away from windows or sources of heat. (For example, if a heating duct runs alongside your closet, don't even think about storing your discs there.) See "Ten Tips for Durable DVDs" for more details about the storage and care of your discs.

If you're truly paranoid--er, cautious--I recommend redundancy. Burn two copies (on two different brands of media, perhaps) and store them in different places. And for truly irreplaceable data, stash an extra copy on a different medium, such as an external hard drive dedicated to this use.

Obviously, if you're burning a music mix CD that you'll be tossing around in the car, the precautions I recommend are overkill. But if you're archiving important data, following the advice outlined in this column can improve the chances that it will endure, and be there when you go back to it years from now.