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Digital
Versatile Disc (DVD) was originally developed for
the consumer electronics marketplace to
deliver audio and video content through home entertainment
systems.
Like its lower capacity predecessor, CD Recordable
(CD-R), originally used to deliver music albums to the
consumer market, DVD was initially developed for the
purpose of delivering high-resolution, full-length movies
to the consumer, and was the next logical medium to
use in place of VHS tapes and VCR players in the home.
As the cost of DVD recording devices and blank DVD-Recordable
media began to fall to the level of CD recording
devices and media, the use of DVD technologies for
the purpose of data archiving and storage gained popularity.
In addition to lower costs, the recording difficulties
and reliability issues that once plagued DVD are
now much less of a factor, making DVD a viable solution
for many data storage applications.
Although current DVD recording devices and media
are significantly more reliable than previous
generations, many compatibility issues still
exist with respect to reading discs in older DVD drives.
This is largely due to the lack of standards
set forth during the early years of DVD technology.
However, to make DVD the most
versatile medium available for data storage,
current DVD drives provide ‘multi-function’ recording
capabilities, offering the ability to read or write
any CD or DVD format.
For applications requiring protection
against deliberate or accidental modification
or destruction of data, DVD
media is available in a Write-Once format. This
particular format, known as DVD-R, is available
in a single-sided disc with a capacity of 4.7GB,
as well as a dual-sided disc with a capacity
of 9.4GB. Single-sided DVD-R is typically used
by home and small office users to archive low
volumes of data. dual-sided DVD-R is more
often used in high-volume data archive environments
that require the use of an automated DVD library
(DVD jukebox) with the capability of flipping
the discs to the alternate side.
For applications that do NOT require storing
data permanently, DVD media is available in
a re-writeable format. This format, known as
DVD-RAM, allows deletions of data and the ability
to re-claim storage capacity on the disc. DVD-RAM,
originally available in 2.6GB (single-sided)
and 5.2GB (dual-sided), now offers the same
capacity as DVD-R, that is 4.7GB (single-sided)
and 9.4GB (dual-sided).
Although the capacities of DVD-R and DVD-RAM
are identical, the physical properties of the
discs themselves are entirely different. Whereas
a DVD-R disc is similar to a CD-R disc, in
that data is written to the disc in a ‘series of tracks’, a DVD-RAM disc
is similar to a Magneto-Optical or Ultra Density Optical
platter, in that data is written to a sector on the
media, much like a hard drive. Because of these differences,
it is likely that the same data written to a DVD-R and
DVD-RAM disc will report differences in space used and
available space remaining on the disc. In addition,
device management software provides significantly different
functionality with respect to the ‘gathering and
burning’ process required to write data to
DVD-R discs vs. DVD-RAM discs.
When choosing DVD as a data archive medium,
automated libraries offer capacities that range
from 470GB to over 20TB of archival storage
in a single library, and can be hosted by any
Windows, UNIX, or Linux operating system. | 
