Ultra Density Optical: Wikis


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Ultra Density Optical (UDO) is an optical disc format designed for high-density storage of high-definition video and data.



An Ultra Density Optical disc or UDO is a 133.35 mm (5.25") ISO cartridge optical disc which can store up to 60 GB of data. Utilising a design based on a Magneto-optical disc, but using Phase Change technology combined with a blue violet laser, a UDO disc can store substantially more data than a magneto-optical disc or MO, because of the shorter wavelength (405 nm) of the blue-violet laser employed. MOs use a 650 nm-wavelength red laser. Because its beam width is shorter when burning to a disc than a red-laser for MO, a blue-violet laser allows more information to be stored digitally in the same amount of space.

Current generations of UDO store up to 60 GB, and a 120 GB version of UDO is in development and is expected to arrive in 2007 and after, though up to 500 GB has been speculated as a possibility for UDO.[1] According to Plasmon, desktop UDO drives are priced at around US $3200. A 30GB UDO Write Once is US $60.[2]


Originally an optical disc storage medium developed as a replacement for the Magneto-optical digital storage medium, Ultra Density Optical was developed beginning June 2000 and first announced by Sony on November 1 2000.[3] It was later adopted with heavy investment by Plasmon, a UK technology company with extensive experience with computer archival backup systems and solutions.[4]

Currently UDO is being championed by its development partners Plasmon, Hewlett Packard, Asahi Pentax (responsible for the opto-mechanical assembly design), Mitsubishi Chemical, parent company of the Verbatim media storage brand, and various computer and IT solutions companies. Mitsubishi Chemical is the second major development partner of UDO media. Due to lack of funding and an economic downturn, Plasmon (Company) closed on November 10, 2008.


Writing technology

UDO uses a Phase Change recording process that permanently alters the molecular structure of the disc surface.

Disc format

There are three versions of UDO 30: a True WORM (Write Once Read Many), an R/W (Re-Writable), and Compliant WORM (shreddable WORM).


The UDO Rewritable format uses a specially formulated Phase Change recording surface that allows recorded data to be deleted and modified. In practice, UDO Rewritable media operates like a standard magnetic disc. Files can be written, erased and rewritten, dynamically reallocating disc capacity. Rewritable media is typically used in archive applications where the stability and longevity of optical media is important, but the archive records change on a relatively frequent or discretionary basis. Rewritable media is typically used in archive environments where data needs to be deleted or media capacity re-used.

True write once

The UDO True Write Once format uses a different phase change recording surface than the Rewritable media. Unlike Rewritable media, the write once recording surface cannot be erased or altered, making Write Once the most stable in terms of data integrity, because the physical record is kept authentic. This level of data integrity is not usually matched by other magnetic disc or tape technologies using normal write once emulation. Write Once has been used successfully in high data integrity environments such as banks and financial institutions with similar magneto-optical discs. Its advantages are media longevity which reduces the cost and frequency of migration, and data authenticity. Common uses of True Write Once media include medical, financial, industrial and applications that have long or indefinite record retention periods with a need for unquestioned record authenticity.

Compliant write once media

UDO Compliant Write Once media has the same operational properties as UDO True Write Once media but with one clear and important difference. Through the use of a specially designed “shred” operation, individual records written to Compliant Write Once media can be destroyed once their retention period expires.

The shred function is controlled at an application level and operates only on Compliant Write Once media. It is a fully verified process and unlike the erase pass on magnetic disks, the shred operation on Phase Change media leaves no trace of any previously written data. While it is possible to shred data on magnetic discs through the use of specialized tools that repeatedly overwrite a patterned sequence, destroying individual records on magnetic tape is not possible without totally rewriting the media.

Magneto-optical comparison

The table below summarizes the differences between conventional Magneto-Optical specifications and those of the enhanced Ultra Density Optical disc.

Disc 5.25-inch UDO Rewriteable 5.25-inch UDO Write Once 5.25-inch MO system (9.1 GB)
Disc diameter 130 mm 130 mm 130 mm
Disc thickness 2.4 mm 2.4 mm 2.4 mm
Cartridge size Same as ISO 130 mm (135 x 153 x 11 mm) Same as ISO 130 mm (135 x 153 x 11 mm) ISO 130 mm (135 x 153 x 11 mm)
Number of physical tracks 96,964 96,964 49,728
Sector size 8 kB 8 kB 4 kB
Number of sectors 2,504,407 2,504,407 1,118,880
Data area 29.0-61.0 mm 29.0-61.0 mm 29.7-62.5 mm
Laser wavelength Violet (405 nm) Violet (405 nm) 660 nm
Objective lens (NA) 0.85 0.85 0.575
Recording layer Phase change Phase change Magneto-optical
Recording format Land & groove Land & groove Land & groove
Recording side Both sides Both sides Both sides
Track pitch 0.33 µm 0.33 µm 0.65 µm
Minimum bit length 0.13 µm 0.13 µm 0.3 µm
Recording density 15.0 Gb/in² 15.0 Gb/in² 3.3 Gb/in²
Transfer rate 4-8 MB/s 4-8 MB/s 3-6 MB/s
Error correction LDC LDC LDC
Modulation RLL (1,7) RLL (1,7) RLL (1,7)


Drive mechanism

UDO Drives Specifications Summary

  • Media Load Time 5 s
  • Media Unload Time 3 s
  • Average Seek Time 35 ms
  • Buffer Memory 32 MB
  • Max Sustained Transfer Rate - Read 8 MB/s
  • Max Sustained Transfer Rate - Write 4 MB/s (with verification)
  • MSBF - Mean Swap Between Failure 750,000 load/unload cycles
  • MTBF - Mean Time Between Failure 100,000 hours
  • Interface Wide Ultra 2 LVD SCSI

UDO comes in both internal and external drive guises. External drives are also available as part a robotic autoloader. All current drives are designed for heavy duty use.

Laser and optics

UDO systems use a blue-violet laser operating at a wavelength of 405 nm, similar to the one used in Blu-ray, to read and write data. Conventional MOs use red lasers at 660 nm.[6]

The blue-violet laser's shorter wavelength makes it possible to store more information on a 13 cm sized UDO disc. The minimum "spot size" on which a laser can be focused is limited by diffraction, and depends on the wavelength of the light and the numerical aperture of the lens used to focus it. By decreasing the wavelength, using a higher numerical aperture (0.85, compared with 0.575 for MO), the laser beam can be focused much more tightly. This produces a smaller spot on the disc than in existing MOs, and allows more information to be physically stored in the same area. [1]

The opto-mechanism design of current Plasmon UDO drives was jointly developed with Asahi Pentax.


Archival storage

Currently UDO has an expected data archival life of around 50 years. Apart from the storage size, the discs (like Magneto Optical discs) are designed for durability and long term reliability. This makes it ideal for backup use in banks, hospitals, governmental and financial institutions.

Secure video

A company called Blu-Laser Cinema announced in June 2005 that it was launching a new player using the UDO format to provide a secure viewing and editing platform for film production houses. Targeted towards the high-end video editing and production community, the unit featured a smart card reader and a USB dongle with an embedded biometric fingerprint reader to allow access only to authorized users.[7]


The core technology for UDO is essentially similar to Blu-ray DVD's, as well as PDDs (all were developed by Sony), although there are a number of key differences; the primary ones being:

Data authenticity and integrity

UDO provides absolute data authenticity for applications where archived information must remain 100% unchanged – banks and legal institutions, for example. UDO uses a phase change recording process that permanently alters the molecular structure of true write once media, ensuring data is integral at the most fundamental level.

Long-term data retention

Long term archival storage. The design of the UDO, with a tested, stable recording surface, protective coating, and encasement in a cartridge, is expected to give it at least 50 years storage life, minimizing the frequency of data migration and management for firms requiring storage for large amounts of important data. The UDO disc design is a robust design and reduces the potential for contamination of media.

High capacity and scalability

Blue laser technology gives the 30 GB UDO more than three times the capacity of previous generation MO (Magneto Optical) and DVD technologies. Being removable, UDO cartridges, combined with off-line media management capabilities typical of optical storage libraries, makes UDO a much more scalable format. Rarely-used data can be removed from a library, freeing up capacity yet remaining managed and accessible.

Rapid information access

UDO has a fast 35-millisecond random access capability. An 8 KB sector size helps read/write performance across a wide range of file sizes. UDO is slightly faster as it operates at Constant Angular Velocity (CAV); during reads and writes, the disc spins continuously at a very high speed. In rewritable applications, UDO has a unique, direct over-write capability, doubling rewrite speeds by eliminating the need for a dedicated erase pass.

Low total cost of ownership

With inexpensively priced 30 GB media, the cost of a UDO library compares favorably with tape or DVD solutions (which can be less reliable than UDO or MO), and systems built around them can be less expensive to operate than certain hard disk-based systems. UDO's ISO standard 5.25 inch media cartridge allows the use of MO and UDO media in the same library, eliminating the need for migration from 9.1 GB MO media. Planned introductions of backward-compatible 60 GB and 120 GB UDO drives make UDO a worthwhile contender for vast amounts of secure storage at a low price.


  1. ^ "Ultra-Density Optical (UDO) Rewritable and WORM Technology". 2006. http://www.optical.com/optical_storage/udo.php. Retrieved 2006-08-25.  
  2. ^ "UDO frequently asked questions.". 2008. http://www.udo.com/faqs/index_right.html#driveprice. Retrieved 2008-02-06.  
  3. ^ "Sony Develops Next Generation Optical Disk Storage System For the Data Server Market". 2006. http://www.sony.net/SonyInfo/News/Press_Archive/200011/00-54E1/. Retrieved 2006-08-25.  
  4. ^ "Plasmon Adopts New High Capacity 5.25 inch Optical Data Format". 2006. http://www.udo.com/docs/pr_udo_nov_announcement.pdf#search=%22ultra%20density%20optical%20development%20history%22. Retrieved 2006-08-25.  
  5. ^ Table from Sony website
  6. ^ "Sony Develops Next Generation Optical Disk Storage System For the Data Server Market". 2006. http://www.sony.net/SonyInfo/News/Press_Archive/200011/00-54E1/. Retrieved 2006-08-25.  
  7. ^ "Sony Develops Next Generation Optical Disk Storage System For the Data Server Market". 2006. http://www.udo.com/docs/udo_cinema_player.pdf. Retrieved 2006-08-25.  

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