Read And Write Speeds
Faster speed means better performance, and better performance typically translates into time savings when ripping multimedia off a disc to your hard drive or onto another disc. However, there are a few caveats and practical issues. First, let’s be clear about speed numbers. A 1x rating on CD-ROMs means 150 KB/s, while 1x on DVDs stands for 1,385,000 bytes/sec, or 1.32 MB/s. These speeds apply to both read and write activity. In theory, a 24x drive is much, much better than a 16x model since it transfers 31.68 MB/s rather than 21.12 MB/s. In practice, it’s not so simple anymore.
On one hand, there’s read speed, which is still limited to 18x for DVD-ROM drives and 16x for most DVD burners. This means that if you already have a drive rated at 16x read speed, it is very likely that a new optical drive won’t deliver any noticeable performance gain. However, new drives are typically slightly quieter and marginally more efficient on power. Read speed is also largely handicapped by an optical drive’s seek time. Repositioning the optical unit above the correct track take time, and access times of 120 to 180 ms can’t be avoided. Hence, reading multiple files distributed across an optical disc takes an inordinate amount of time.
On the other hand, there’s write speed, which is what the industry usually focuses on. Write speeds have progressed recently from 16x to 20x and now 24x in an effort to reduce DVD-5 write times. Single-sided, single-layer DVD-5 discs have a 4.7GB capacity, while single-sided double-layer DVDs (8.5GB) are known as DVD-9. Unfortunately, these fast write speeds only apply to single-layer discs. The good news is that a DVD-5 disc can now be finalized in just over four minutes, but it still takes more than 16 minutes to write a DVD-9 disc with less than twice the capacity. DVD-9 write speeds are still limited to 12x.
Unfortunately, there are issues with high-speed recordable DVDs, and 24x single-layer or 12x double-layer media is hard to find. Be prepared to spend much more than you would for 16x single-layer or 8x double-layer media. High-speed DVD recording isn’t a myth, but it’s exclusive to say the least. In addition, write quality is an issue at high recording speeds. Since the laser burns pits into the recording surface, it is increasingly difficult to ensure proper recording accuracy given that vibration increases dramatically at high-RPM speeds. Although we don’t have the resources to perform detailed media analysis in-house, such evaluations by others make it obvious that you should avoid the highest recording speeds if you want to ensure a long life expectancy for your recorded discs.
Since prices for external hard drives and USB sticks have fallen quite a bit, we decided to leave rewriteable media out of this analysis. There might be scenarios in which using DVD-RW or DVD+RW makes sense, but a fast USB stick is typically more convenient—and faster. The conventional DVD-R or DVD+R, however, has its place given that written data can’t be modified unless you physically damage the disc.
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