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IntroductionThe Demand for Data Storage

It is estimated that 250 megabytes of information is produced every year for each man, woman, and child (1 to 2 exabytes in total.)

Printed documents make up only .003% of this total.

History

Today’s Storage Technologies

Magnetic storage Optical storage Magneto-optical (MO) Solid state storage

Magneto-Optical Storage

Combines magnetic disk technologies with laser technology.

Can be read and written to over one million times.

Portable. Capacity is 2GB or more per disk. Faster than floppies and CDs, but slower

than hard drives.

CD-ROM

Works by reading bumps and low spots, or pits and lands on a disc with a laser.

Discs contain three layers: plastic, aluminum, and acrylic.

Aluminum layer reflects laser light, a detector can determine the difference between a pit and land.

CD-RWDisc Layers

Dual-Layer

Has two layers of data One layer is semi-transparent Laser can focus through it

Read the second layer Both layers are read from the same side Advantages:

– Hold twice as much as a single-layer disc– Long movies use higher data rates for better quality

DVD

Digital Versatile Disc / Digital Video Disc Red laser Backward-compatible with CD-ROMs Formats

– DVD-ROM– DVD-R/RW– DVD+R/RW– DVD-RAM

DVD-ROM

Works same as CD-ROM, but bumps are smaller and packed closer together.

Contains less error correction information (better error correction algorithm than CDs.)

Supports double layer storage, effectively doubling the storage area.

Drive does not spin at a constant speed which allows a constant data rate stream.

Blu-ray Disc (BD)

Developed by Blu-ray Disc Association (BDA) Recording, rewriting and playback of HD Blue-violet laser BD formats planned

– BD-ROM– BD-R– BD-RW

On a 25GB disc– 2 hours high-definition television (HDTV)– 13 hours standard-definition television (SDTV)– Take about 1 hour and 33 minutes

Blu-ray Disc

CD capable of storing 27GB. Uses blue laser as opposed to current red

laser. Blue laser can focus on smaller area,

allowing more information to be stored in a given area.

Blu-Ray Disc

Phase Change Recording

Type of recording technology Enables the disks to be written, erased, and rewritten Developed in late 1960s by Stanford Ovshinsky Involves a high intensity laser beam heating a

recording layer Alternate between an amorphous (formless) and a

crystalline state

Phase Change Recording

Alloy recording layer is a mix of silver, indium, antimony and tellurium

After heating to one particular temperature, the alloy will become crystalline

To erase or write over recorded data, the higher temperature laser is used, which results in the amorphous form

Used for both CD-RW, DVD-RW, DVD+RW and DVD-RAM

Blu ray vs DVD Capacity

DVD Vs Blu-Ray Construction

Benefit of using a blue-violet laser (405nm) Higher storage capacity

– Shorter wavelength than a red laser (650nm)– Focus the laser spot with greater precision– Data can be packed more tightly and stored in less space

Faster data transfer rate Support more formats of video compression

Blu-ray vs. HD DVD vs. DVD

Parameters BD HD-DVD DVD

Storage capacity 25GB/50GB 15GB/30GB 4.7GB/9.4GB

Laser Blue-violet laser Red laser

Laser wavelength 405nm 405nm 650nm

Numerical Aperture (NA) 0.85 0.60 0.60

Protection layer 0.1mm 0.6mm 0.6mm

Data transfer rate 36Mbps 36Mbps 11.08Mbps

Video compression MPEG-2MPEG-4 AVC

VC-1

MPEG-2MPEG-4 AVC

VC-1

MPEG-2

BD Disc and Recorder

Sony BDZ-S77 $2,150 $26 per disc Available in Japan only

– HDTV is not well established

Wait until 2006-2007

HD-DVD

High-definition or High Density DVD Also known as Advanced Optical Disc (AOD) Proposed by NEC/Toshiba Use the original DVD physical format Depend on new video encoding technology Use blue or violet lasers to read smaller pits Backward-compatible with DVD

Summary

Demand continues to grow. Cost per megabyte is decreasing. DVDs replacing older technologies. Convenience, cost, acceptance, and capacity

will drive new products. Several new technologies on the horizon,

providing reduced sizes with increased capacities and data transfer rates.

Conclusion

Reference

Websites– http://www.blu-ray.com/– http://www.dvddemystified.com/– http://www.howstuffworks.com