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Introduction
Overview of CD-RW Technology
How many times can a CD-RW disc be overwritten?
- Create
Your Own CDs
- Archive
Your Creativity
- Exchange
Ideas
- Back
up Your Data
- Achieve
Speed Performance
CD
Recording has become one of the most popular formats for the
quick exchange, urgent replica, and long-term archiving of business
& consumer data. With the widespread adoption of CD Recording
technology, has come the long awaited release from the restraints
of the ubiquitous floppy drive. For those who replication needs
are mixtures of high volume but lower capacity, recordable CD-ROM
media is an ideal solution.
Recordable CD-ROM media has also assisted in eliminating one
giant and further headache known to most people who have at
one time needed to backup data: the dreaded compatibility issue.
Multiple
storage platforms, diverse operating systems, and incompatible
file systems, caused havoc for businesses attempting to exchange
data quickly and simply.
In
the media industry the SyQuest disks and drives appeared in
every corner and everyone needed one (usually a new one every
couple of months as reliability was not one of its strongest
points). The drive and media cost was high in comparison to
CD technology, and the platform was not known for its stability.
CD writing changed this picture dramatically. With blank CD
starting at under £1, and drives under £200 (even
for SCSI units), CD writers have given the industry exactly
what it needed. Cheap media, internationally compatible standards,
and a CD-ROM drive for data reading in even every cheap computer
in the world.
The CD Writer has come a long way in a very short space of time.
The first single-speed models may be only a couple of years
old, but already they seem like ageing dinosaurs from a half-forgotten
era.
CD Rewriters expanded the market even
further, and with 4xspeed, then 6xspeed and beyond CD Writers
soon popping over the horizon (and with prices dropping faster
than even RAM ever tried to in its heyday), CD Recording has
become a normal and simple process for countless computer users.
Next Generation
Fast on the heels of the CD Recording systems in the portable
storage race is DVD technology. DVD recorders in the guise of
DVD-RAM, DVD-R, DVD-RW, PD, and a host
of other standards are encroaching into this once unassailable
territory.
The choices suddenly don't seem so clear-cut anymore. Which
technology are you better off with? Which version of optical
platter technology should you select? The choices can be narrowed
down far more simply and quicker than they seem at first sight.
Recordable
CDs can be written to support a number of standards and platforms.
From Audio CD, Data CD, to Video CD, writing your own CD's opens
up a realm of possibilities. Standard supported formats would
include:
-
High
Sierra
-
ISO
9660
-
RockRidge
extension
-
Joliet
-
Multi-session
-
DVD
disc with ISO reader
-
UDF
discs
-
HFS
For
a more detailed view on these and other CD standards, please click
here.
CD-RW discs use a phase-change technology enabling
the discs to be written and rewritten to many times. The recording
layer here is completely different to that of CD-R. It is constructed
of a polycrystalline mixture of silver, indium, antimony, and
tellurium. During the recording process the laser heats areas
of this layer to 700 degrees C, and the crystals melt into an
amorphous (non-crystalline) phase which is stabilised by quick
cooling. The reflectivity of the amorphous area is much lower
than the crystalline layer, so the drive can read it as a pattern
of pits like a regular CD.
When re-formatting the disc to erase the data, the laser heats
the amorphous areas at a lower intensity to just below melting
point, long enough for crystals to reform. This can be repeated
a thousand times or more, making the CD-RW disc as usable as a
high density floppy.
How many times
can a CD-RW disc be overwritten?
In the specification a minimum of 1,000 cycles
is put down. The specifications of the individual media manufacturer
may be higher. Some manufacturers are expected to achieve up to
10,000 cycles and we'll look for improvements in the future. Note
that the user will rarely notice this phenomenon because it is
handled by the application software in a transparent manner. Besides
that sectors that may be degrading are being avoided by intelligent
file systems such as UDF.
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