Optical Storage - Upgrading and Repairing PCs - page 700

In the past, I have been opposed to DVD-RAM because of a lack of compatibility with
other drive types. However, if you use drives supporting the DVD Super Multi standard,
you can read and write DVD-RAM as well as other rewritable DVD formats. With the
abilitytoread,write,anderasedatawithouttheneedtouseUDFpacket-writingsoftware,
DVD-RAM can be a useful alternative to other types of rewritable DVD—assuming all
your drives can use it.
DVD-R
DVD-Risawrite-oncemediumsimilartoCD-R,whichwasoriginallycreatedbyPioneer
and released by the DVD Forum in July 1997. You can play DVD-R discs on standard
DVD-ROM drives. Some DVD-RAM drives can also write to DVD-R media.
DVD-R has a single-sided storage capacity of 4.7GB—about seven times that of a CD-
R-and double that for a double-sided disc. These discs use an organic dye recording layer
that allows for a low material cost, similar to CD-R.
To enable positioning accuracy, DVD-R uses a wobbled groove recording, in which spe-
cial grooved tracks are preengraved on the disc during the manufacturing process. Data is
recorded within the grooves only. The grooved tracks wobble slightly right and left, and
thefrequencyofthewobblecontains clockdataforthedrivetoread,aswellasclockdata
for the drive. The grooves are spaced more closely together than with DVD-RAM, but
data is recorded only in the grooves and not on the lands (see Figure 11.14 ) .
Figure 11.14 DVD-R wobbled groove recording.