It’s been a long wait but the blue laser finally makes its entrance as the next step in the evolution of optical storage. Despite being mooted back in the days of dual speed CD-ROM drives it’s taken over ten years for the first viable products to emerge and Plasmon’s UDO (ultra density optical) drive targets archival storage in the mid- to enterprise-level markets. However, before looking at the drive it’s worth stepping back and running through the technology first as UDO isn’t the only blue laser product currently on the market. Sony has also released its PDD (Professional Disc for DATA) drive and Blu-Ray drives are also coming on-stream in the Japanese market as well.

Blu-Ray technology is at the foundation of each product and uses a 405nm blue-violet laser but beyond this things start to diverge rapidly. True Blu-Ray products are aimed at the consumer market and primarily target recording, rewriting and playback of high-definition television (HDTV) with the 27GB disks capable of holding two hours of HDTV or thirteen hours of normal TV. PC storage applications are expected to be supported but this is a secondary aim of this technology.

The biggest difference is with the lens. Whereas Blu-Ray and PDD lasers both have a numerical aperture (NA) of 0.85, the UDO lens has a smaller NA of 0.7. Equivalent to a photographer’s f-number this results in a larger laser spot and a corresponding reduction in storage capacity. Blu-Ray and PDD offer 27GB and 23GB respectively on single sided discs whereas Plasmon opted to go for double sided discs with 15GB per side. Plasmon’s reasons for using a 0.7NA lens were reduced manufacturing costs and higher reliability. A general drawback for all blue laser products is the reduced depth of field as the lens must be moved closer to the disk so it can focus on the recording surface. Consequently, a protective substrate thickness of a mere 0.1mm is insufficient to protect the disc so it must be enclosed in a protective shell at all times. An extension to the Blu-Ray specification calls for an optional cartridge but research into an extra-hard shell is still ongoing.

One of the key differentiators of UDO is the physical format as Plasmon required compatibility with MO (magneto optical). Consequently, the drives have the same dimensions and the cartridges are exactly same form factor so will fit in MO loader mechanisms. This is to ensure that MO and UDO drives can be mixed and matched in the same library allowing business to migrate easily to the new format. However, it is important to understand that the formats themselves are not compatible as UDO drives cannot read MO media.

Installation of our early sample proved to be problematic thanks to Plasmon’s insistence on using 8KB disc sectors. At the time of writing the drive is only supported by Windows 2000 and XP systems that have the KB831293 hotfix applied. This stops the system crashing with an error due to a conflict with the Windows memory page file size. We were advised that no patch is currently available for Windows Server 2003 and testing confirmed that the act of loading a UDO disk under this OS will cause a blue-screen failure.

Note also that the drive can only be used with supported Windows versions once the bundled Software Architects utility has been installed which allows it to function with rewritable media only. Plasmon’s Diamond software also allows the drive to be used as a standard disk drive but it must also be installed if you want to use the True WORM media. UDO performance is lower than that quoted for PDD and our tests with Iometer returned 4.7MB/sec and 2.6MB/sec for read and write operations respectively. We confirmed these results by writing a 690MB video file to the UDO drive and reading it back which returned 2.5MB/sec and 4.3MB/sec.

Unusually, the target markets for the current crop of blue laser products are very clearly defined. Blu-ray is for consumers and Sony has aimed PDD at the small to medium business. Consequently, UDO is currently the only choice for mid-sized businesses and enterprises looking to upgrade capacity of their MO-based archival systems.


Optical storage is the natural choice for data archiving as it offers an unbeatable shelf-life. Enterprises currently using MO must know that this format is at the end of the road and, despite the sector related issues, UDO offers the best method of migrating to higher capacities without trashing existing investment in MO libraries.