OSD Data Storage Technology

Optical Super Density (OSD) technology’s design goals were to develop a high capacity (40GB or more) removable MO drive which retained the ruggedness and reliability offered by today’s ISO-standard MO solutions, achieve data transfer rates competitive with hard disk and tape products (30 MBps) and provided the user a significantly lower cost per megabyte than other optical and tape products. In the spring of 1999, following 18 months of co-ordinated development with its media and optics partners, Maxoptix Corporation – a leading manufacturer of Magneto Optical storage solutions – announced the successful demonstration of its Optical Super Density (OSD) technology.

Achievement of Maxoptix’s design goals relied on a number of innovative technologies:

  • OverCoat Incident Recording: Developed to overcome the restrictions of the substrate incident recording technique used in traditional ISO-standard MO, the OCIR architecture has the recording layer on top of the substrate – like a hard disk – but also a thick transparent acrylic overcoat – similar to the coating on the back of CD and DVD media – protecting it. The OSD coating is more than 1,000 times thicker than that of hard disk and tape products, but much thinner than the substrate used on today’s ISO media. Since it allows the lens to be positioned much closer to the recording surface, OSD is able to use a higher numerical aperture lens, resulting in much higher data densities. OCIR also provides media durability and very long media shelf life, it being estimated that OSD media will provide millions of read/writes and more than 50 year data integrity. OSD media will be sold in a cartridge very similar to conventional MO media and will be compatible with existing automation in today’s ISO-standard jukeboxes. This means today’s MO jukeboxes will be able to upgrade to OSD drives and media for an almost 800 percent increase in capacity without requiring changes to the jukebox mechanics.
  • Surface Array Recording: OSD products will incorporate independent read/write heads on both sides of the media and utilise a technique known as Surface Array Recording (SAR) to allow access to both sides of the disk simultaneously. This contrasts with traditional MO, where users are required to flip the media in order to read data stored on the opposite side of the disk. By providing simultaneous read or write to both sides of the media, SAR not only doubles the on-line capacity, but also allows data rates comparable with hard disk products.
  • Recessed Objective Lens: The Recessed Objective Lens (ROL) is designed both to enhance the head/disk interface’s immunity to contamination and to allow for continuous focus of the objective lens. Because the objective lens is recessed above the magnetic head it will not be subjected to particulate contamination that may be introduced into the drive during media insertion. Further resistance to contamination is provided by Maxoptix’s innovative Air Clear System (ACS) which produces air flow through the magnetic head and prevents contamination from collecting in the light path. By decoupling the objective lens from the magnetic head in the vertical direction OSD drives are able to perform continuous focus and tracking by controlling the exact height of the objective lens over the media under servo control. This improves the reliability of the drive by allowing it to adapt to a wider range of environmental conditions.
  • Magnetic Field Modulation: Magnetic Field Modulation (MFM) removes the limitations inherent in traditional MO drives use of a coil to write data. By utilising a small magnetic head in close proximity to the disk, the polarity of the magnetic field can be switched at a very high frequency. The quick changes in polarity produce marks on the disk that are narrow and tall, often referred to as crescents. These crescent shaped marks provide a significant increase in bit density, therefore the bit density is no longer limited by the wavelength of the laser. Also, because the polarity of the field can be switched fast the disk can be written in a single pass.
  • Magnetic Super Resolution: The use of MFM shifts the limiting factor on bit density from the wavelength of the laser to the ability to resolve individual marks during read using a spot that may cover several marks. Magnetic Super Resolution (MSR) is a masking technology that enables read back of very high bit densities by isolating the individual bit to be read. During the read process, more energy is applied to the disk to pre-heat what is referred to as a read-out layer that lies on top of the recording layer. The read-out layer magnifies the bit area providing higher resolution for progressively smaller bits. This increases not only the capacity, but also the performance.

Production is expected to begin during 2000 and will initially be targeted to replace various tape products in the high-performance, high-end data backup/archive applications. OSD is expected to complement existing MO solutions, not replace them. In addition to high capacity, OSD drives will offer MO-like high reliability and ruggedness, making them suitable for the harshest environments. The removable OSD media is also virtually indestructible, can be overwritten 10 million times without data degradation and provides as much as a 50-year shelf life. Whether as a single drive or integrated into jukebox environments, OSD will provide a high-performance solution for single desktop, workgroup, departmental, network and enterprise-wide storage and retrieval requirements.

The ruggedness and exceptional reliability of the OSD media are optimal for applications such as: data warehousing/mining, back-up/disaster recovery, network backup, document imaging, Computer Output to Laser Disk (COLD), Hierarchical Storage Management (HSM), Internet content storage and multimedia applications including video/audio editing and playback.