ST1901

TECHNOLOGY FOCUS: OPTICAL DISC
the reliability of this storage method.
DATA EXPLOSION
As shown in Figure 1 (below right), due to
the popularisation of IoT, the explosive
growth of data is expected to exceed the
storage capacity available to the world. The
result is that valuable data is being
discarded and lost. This dramatic growth in
demand for data storage combined with the
nature of this data - often referred to as
Cold Data as it has low access frequency
requirements and is stored for a long period
of time - necessitates a change in how we
store this data from now on.
ARCHIVAL GRADE
Optical discs are still one of the most
popular forms of storage media in the
world; for consumer applications, but also
for business purposes, administrative
materials and research materials in
museums, libraries, and archives.
For optical discs used for archiving, the
reliability of the storage method and media
is critical. Long-term preservation of data
can be realised by combining longer
lifetime optical discs, called Archival Grade
Optical Media, which has proven higher
reliability than regular optical media,
together with a dedicated optical drive.
addition, a dedicated recording drive is
used and a specific recording method is
adopted that draws out the best
performance. There is also a drive
employed that measures the quality of the
recorded signal and periodically checks the
quality of the recording.
The optical media industry has benefited
hugely from the adoption of international
standards developed by ISO and JIS to
ensure wide compatibility. Table 1 (above)
shows the three standards that are used:
Format Standard, which ensures
compatibility with the drive used for
recording or reproducing the data; Lifetime
Measurement Standard, a test to assess the
likely longevity of the media, and
Operational Standard, which guarantees
It has been reported that optical media
using a stable inorganic material recording
film can last for several hundred years - or
even several thousands of years - when kept
at a temperature of 25°C and a relative
humidity of 50%. Also, using the
parameters obtained by the lifetime
specification and the Eyring formula, the
estimated lifetime at different temperatures
and humidity can be obtained.
For example, even at a temperature of
35°C and a relative humidity of 50%, the
estimated lifetime is over a hundred years,
and it can be presumed that data can be
stored and managed for a long period of
time even in a rough storage environment.
Based on all of this evidence, it is possible
to significantly extend the data migration
interval which is carried out every three to
five years on a normal hard disk, by using
archival optical discs instead.
In optical disc library systems, power is
not needed except during recording and
reproduction, so the amount of energy
required and generation of heat is very
small. Therefore, the use of archival optical
discs make it possible to suppress energy
For archival optical discs, Mitsubishi
Chemical Media, which also owns the
popular Verbatim brand, has improved
resilience by using more durable materials
compared to consumer optical discs, and
strict quality control standards with tighter
specifications to remove variation. In
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Jan/Feb 2019
STORAGE
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