Decoding Recordable DVD

By Robert Starrett  |  Posted 2003-01-01

Decoding Recordable DVD

DVD burning is a very appealing idea. You get a whopping 4.7GB of space to store backups, make movies, and more. CD burners are fairly common in new PCs, but the rapid adoption of DVD readers and players, and the skyrocketing capacities of hard drives, are starting to make the roughly 700MB storage limit of CDs look downright puny. DVDs are much more suitable for copying videos, distributing homemade movies, or backing up and archiving your data. And prices of DVD recorders, while still significantly higher than those of CD-RW drives, are falling rapidly. But you may be confused (and rightly so) by all the formats for writable DVDs. The options can seem overwhelming: DVD-RAM, DVD-R, DVD-RW, DVD+SC, and DVD+RW are all competing for market attention. Whats the difference? And which is best for your needs?

Format Confusion

Format Confusion

All the write-once (R) and rewritable (RW) DVD versions make a daunting puzzle. Pioneer released a DVD-R drive in 1997, but the device wasnt affordable. Rewritable DVD-RAM first appeared in 1998, but its initial iterations werent compatible with computer DVD drives. The DVD-RW standard wasnt completed until early in 2001 and wasnt universally accepted. Most recently, a few notable electronics companies introduced the DVD+RW and, later, the DVD+R formats, which promised greater compatibility with standalone DVD players. To make sense of this mess, lets break it down by drive type and medium.

DVD-RAM drives, much like magneto-optical drives, use a disc enclosed in a cartridge. But standalone DVD players and DVD drives dont accept cartridges, so DVD-RAM discs could not be read in anything other than DVD-RAM drives. This changed with the advent of the Type II DVD-RAM cartridge, which let you remove the disc and insert it into a DVD player or a computer DVD drive. Not all DVD-RAM drives accept Type II cartridges, though, so check the specifications of any units youre considering if youre shopping for this type of drive. The capacity of DVD-RAM media is either 4.7GB or, for double-sided cartridges, 9.4GB.

DVD-RAM cartridges claim to allow 100,000 rewrites. This is great for backup purposes, because you can treat the DVD-RAM drive like any other drive, and you have plenty of room for data. Incidentally, some newer DVD-RAM drives can record to DVD-R, CD-R, and CD-RW discs (without a cartridge). DVD-RAM drives can also play all CD formats.

Industry experts say that DVD-RAM is losing ground to the other rewritable DVD formats, and that it may fade from the market as the competing standards vie for dominance. Moreover, new combination drives support both "dash" and "plus" standards—but not DVD-RAM.

Drives labeled DVD-R/RW record to like-named media and also to write-once and rewritable CDs; they read all CD formats, too. DVD-RW discs allow up to 1,000 rewrites and hold 4.7GB. This format has been around a little longer than its main competitor, DVD+R/RW, and has thus gained wider acceptance in the DVD-authoring and DVD player categories.

DVD-RAM and DVD-R/RW have been approved by the DVD Forum (which includes Hitachi, JVC, Philips, Pioneer, Sony, Toshiba, and many more). But because the group is not a standards-setting body, approval is meaningless in any practical sense. ECMA, the European Computer Manufacturers Association, has approved all DVD–recordable formats, including DVD+R and DVD+RW.

The main developers of DVD+R/RW are HP, Philips, and Sony, who felt that this technology was superior to existing ones (hence the plus sign). The drives record to DVD+R and DVD+RW discs, but not to DVD-R or DVD-RW media. The standard is not endorsed by the DVD Forum. DVD+R/RW media also hold 4.7GB and can tolerate up to 1,000 rewrites. Dash and plus double-sided discs—which you have to turn over—are just becoming available.

Plus drives work at least as well as dash drives, and some features may make them faster and more reliable than their counterparts. For example, DVD+RW drives record at faster rates than most DVD-RW units. Some DVD-R discs can be written at near DVD+R speeds, though, and recently announced DVD-RW models should narrow the speed gap further.

Another difference between dash and plus technologies involves the way the drives spin discs. CD, DVD-ROM, and DVD-RW drives are constant linear velocity (CLV) devices, which maintain constant data-transfer rates when reading discs. These drives rotate discs more slowly when reading near the outside edges, where there is more physical surface in each track. Faster drives use CAV (constant angular velocity), keeping the rotational speed constant and using a buffer to deal with the differences in data readout speeds. CAV is particularly important for PC users, as it allows for higher-speed DVD and CD reading. DVD+R/RW drives support both CLV and CAV. In addition, plus drives dont require session closing and finalization when burning discs. All this translates to a slight speed advantage for DVD+R/RW.

Now lets throw in a fourth drive type to complete the picture: the combination drive. This type records to all of the dash and plus formats (but not to DVD-RAM) in addition to CD-R and CD-RW. The Sony DRU-500A ($350 street) is one such drive.

Competition and Compatibility

Competition and Compatibility

Despite DVD-RAMs early arrival to market and the advantage of 100,000 rewrites, it will probably end up in niche applications—network data backup, for example—not on the average users desktop.

Whether plus or dash is superior technologically is hard to say; manufacturers are constantly improving the speed and compatibility of their drives. But with Sonys combo drive priced just slightly higher than the current dash and RAM drives, other manufacturers will likely offer combo drives at similar prices soon.

Whether youll ultimately use dash or plus in recording depends on compatibility—will the recorded discs work with your DVD drive and your DVD player? If you can, try the burner before you buy. Most computer DVD drives and burners can read DVD-R/RW and DVD+R/RW discs. Earlier DVD drives (those around four years old) may not be able to read every format. DVD-R and DVD+R discs will work in most current DVD players, but some players have trouble with the rewritable versions of these formats. For backup, however, you can use DVD-R/RW and DVD+R/RW with confidence.

Backup to DVD

: Ten Software Features You Need "> Backup to DVD: Ten Software Features You Need

Backup Now! 3 DeluxeBecause of the large capacities of DVDs, DVD burners are tempting alternatives to tape or CD-RW drives for backups. But youll need some software to ease the task. Backup NOW! 3 Deluxe, from NewTech Infosystems ($79.99 list — Check Prices,, stands out as a particularly easy-to-use utility. Dantz Retrospect Pro ($129 list — Check Prices, and Veritas Backup MyPC ($79 list — Check Prices, are also strong contenders.

Heres an outline of the features you should look for when shopping for a backup program.

  • Device support. This may sound obvious, but make sure the program supports your DVD drive. Optimally, your backup software should support all DVD formats. Some programs include support for CD, magneto-optical, Jaz, Zip, and network drives, too.
  • Software support. Find out if the publisher makes free driver updates available as new recorder models are released. Make sure you understand the vendors tech-support policy.
  • Incremental and differential backup capabilities. Full backups are necessary, but take too much time to do every day. Once you have made a full backup for the week, say, your software should be able to back up just the files that have changed each day.
  • Image backup. The software should be able to back up everything as one large file thats a bit-for-bit duplicate (an image) of your hard drive.
  • Bootable disk support. Your software should be able to create a bootable disc to ensure recovery in case of a system crash. Although you can make bootable floppy disks even for Windows 2000 and XP, using the backup software to create the bootable disc makes recovery and restoration easier, because the boot routine will be specific to the backup program.
  • Automatic backup scheduling. You shouldnt have to be around to make backups. Simply set the backup schedule and let it run when the machine is not in use.
  • Password protection. For security, the software should let you password-protect your backup discs so even a stolen set cannot be restored.
  • Disc spanning. The program should be able to spread a large backup over several discs. With 40GB, 60GB, and 80GB drives common, even a 4.7GB DVD may not be enough to hold a full backup of your hard drive.
  • Data compression. Depending on file type, the software should be able to squeeze the raw data 30 to 40 percent and even more in some cases. This should be an option, though; not everybody is comfortable with compressed files.
  • Drive spanning. This is a useful but not necessary feature. It lets you back up to multiple recordable drives if you have them. Using three or four DVD-RW drives, for example, you can make a spanned disc set without having to change media in mid-backup.

    Bob Starrett is a freelance writer and consultant who has coauthored five books on CD technology.

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