DVD Basics
There are DVD-ROM drives (Read Only Memory) and DVD burners (writers, recorders). Both read all types of DVD media, but only DVD burners write onto compatible discs. Data is read or written from or to the dye layer using a 650-nm wavelength. DVD-R by the DVD Forum was the first DVD standard, but it wasn't quite accepted by all device manufacturers, because it carried sectors which could not be written for the purpose of preventing illegal copies of copyrighted material. Some industry members them founded the DVD+RW Alliance, which developed its own standard. It's incompatible, but technically similar.
While the first DVD burner generations only supported one of the two standards, today's drives are capable of handling both (although only DVD-R products may carry the DVD logo) and there is no price difference between DVD-R and DVD+R anymore. Also, it doesn't matter which standard you use for data storage.
Single-layer discs are incredibly inexpensive and can be written in fairly quickly in five to six minutes at 16X write speed. The double-layer media (DL) is still somewhat expensive and requires at least 20 minutes to finish the 8.4 GB task. This is because the write speeds max out at 10X for DL, and the two layers have to be written consecutively.
Most DVD burners still use an UltraATA interface, but more and more devices come with modern Serial ATA interfaces. SATA has the advantage that you don't have to configure anything - just plug the device into an available SATA port. UltraATA devices require a jumper to be set to determine whether the drive runs in master or slave mode.
Performance Basics
There are two different ways of operating drives that are based on rotating media. This can be at constant angular velocity (CAV) or constant linear velocity (CLV). Hard drives typically operate at a constant angular velocity, which means that the absolute velocity increases towards the outer areas of the rotating platter by maintaining a fixed rotation speed of e.g. 7,200 RPM. Optical drives such as CD or DVD drives utilize either the technology, or a combination of both technologies, called PCAV (partial constant angular velocity). And there is the option of running drives in ZCLV mode, which holds a certain speed for a given zone on the disc.
While rotation speeds are very important, vibration is a serious issue that requires attention. For this reason, many drives have vibration sensors, which throttle media rotation speeds in case of read or write failures.
Optical drives show considerably slower access times than hard drives. Typically, the laser unit is driven by a small motor, guided within a little concentric rail. The results are access times that are at least 10 times longer than with hard drives. But as many applications for DVD storage require sequential reading of information, access time can be considered secondary.
Lightscribe
Labeling your own DVD is an interesting topic. The typical approach is to use a thin, permanent marker to write your title on the upper side of the DVD. This can be done with most DVDs you buy in retail channels. However, this doesn't look very professional. LightScribe is a technology that uses a drive's DVD laser unit that allows you to etch text or images onto the surface. As you can imagine, LightScribe requires appropriate recordable media and you have to insert your DVD upside down to be able to "lightscribe" it. More information can be found here.
