Magneto Optical Disk

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Storage medium
Magneto Optical Disk
MO OLYMPUS OL-D640.jpg
Olympus magneto-optical disc with 640 MB
General
Type magnetic
capacity 128-16,700 MB
size 90 mm (3.5 ″) / 130 mm (5.25 ″)

The magneto-optical disk ( MO disk also MOD , dt. " Magneto- optical disk") is a rotating storage medium that is written to magnetically and read out optically.

There is no uniform notation for the magneto-optical disc. You can find both Magneto-Optical Disc / Magneto Optical Disc and MO disk or MO for short . The latter is also available in the popular variants MO drive and MO medium (or more rarely) MO cartridge .

Magneto-optic technology

While all other types of recording use either magnetic (e.g. hard drives ) or optical methods (e.g. DVD ), magneto-optical technology combines both methods.

The recording is done magnetically. However, the material of the MO disks is not magnetizable at room temperature. This is only possible above the Curie temperature , so that the material has to be heated so that it can be magnetized. A laser beam is used for this. The advantage is that the media are insensitive to magnetic fields and the magnetization is retained even after long storage. The magnetization is, so to speak, permanently frozen.

The differently magnetized areas reflect light differently due to the magneto-optical Kerr effect , so that a laser beam with optics with a Wollaston prism can also be used for reading . This has a low output because it does not have to or should not heat the material.

Before writing, an erasing process is also necessary, which is also implemented by heating the track above the Curie point. In the case of special overwrite media (recognizable by the “OW” logo, known by the addition of LIMDOW at Fujitsumedien), the deletion process is superfluous; it is written without prior deletion. This doubles the writing speed. The drive must support such overwrite media.

Specification of the media

Knowing the specification of the disk is useful when evaluating MO technology and purchasing MO devices and media. In the following, only the information that is of immediate general interest is presented. Purely technical details can be found in the sources, see chapter Standards .

Appearance
The MO media are permanently housed in a protective sleeve that resembles a 3.5 ″ diskette . This protective cover is also known as a cartridge . A 3.5 ″ MO medium is roughly twice as thick as a 3.5 ″ floppy disk.
diameter
The MO media are available in two different diameters: 90 mm (corresponds to the 3.5 ″ form factor) and 130 mm (which corresponds to the 5.25 ″ format).
Storage capacity
The storage capacity of the MO media depends on the diameter, track density, bit density and sector size. The following capacities are common, although the smaller ones are only available to support older drives:
throughput
knife 		Sector size
[bytes] 		Storage capacity
[MB]
3.5 ″ 0512 128, 230, 540
3.5 ″ 2048 640, 1300, 2300
5.25 ″ 0512 650-9100
5.25 ″ 1024 650-9100
5.25 ″ 2048 5200-16,700
5.25 ″ 4096 up to 9100

Differences between the MOD and a DVD-RAM

An open MOD whose sectoring can be seen with the naked eye
A DVD-RAM has the same (visible) sectoring as a MOD.

In literature and practice, MO is occasionally compared with DVD-RAM . Both storage media have the common feature of sectoring (see figures), but otherwise they have little in common due to their different recording methods (optical or magnetic).

In addition to these fundamental differences, DVD-RAM and MO differ in terms of storage capacity, media prices, transfer performance and distribution. A current 3.5 ″ MO disk has a maximum of 2.3 GB, a DVD-RAM 4.7 GB. In terms of price, a 2.3 GB MO disk costs around € 16 and a 4.7 GB DVD-RAM medium costs around € 2.40 (as of May 2007). The transfer data rates of DVD-RAM drives are superior to those of MO drives. MO systems are more likely to be found in professional IT areas, whereas a DVD-RAM burner is affordable for everyone these days.

The MOD is recognized by newer operating systems as a hard disk , while the DVD-RAM is only integrated as a DVD burner in a few individual cases . If a DVD-RAM drive is recognized and installed as a DVD burner, it can then only be written to with any packet writing software. In addition, depending on the operating system, a DVD-RAM burner can also be addressed via a DVD-RAM device driver as a removable medium that may be restricted under certain circumstances. With current operating systems, a DVD-RAM is also operated like a hard disk or floppy disk.

When formatting the DVD-RAM with FAT32 , the burner works like a hard disk. Files can be copied or dragged and dropped onto the open medium and are written immediately.

Compared to DVD-RAM, MOD has higher physical data security (reliability) because

  • MO media are completely insensitive to light
  • MO media are insensitive to temperatures up to approx. 100 ° C
  • MO media are completely insensitive to magnetic fields at normal temperature
  • the magnetic information on MO media is insensitive to strong acceleration forces
  • Current MO media are always surrounded by a protective plastic cover ( cartridge ), while DVD-RAM media, depending on the reader, are increasingly being used without a cartridge, which increases the risk of damage (e.g. scratches) during use.
  • MO media always have a mechanical write protection switch that reliably prevents deletion due to incorrect operation or defective software.

Hazards

Operating systems such as Microsoft Windows write parts of the data carrier over and over again with every system start, with every check or with every new entry in individual places (sectors), so that the data carrier is retained for a long time and its data content remains undamaged, but for example Directory of stored data can no longer be read. MODs must therefore not be operated in permanent system access without write protection if such defects are to be avoided.

Similar techniques

The audio medium MiniDisc from Sony uses the same technology as MO drives.

An iDPhoto (ID-Photo) is an MO disk and was introduced to the market by Sanyo in 2000.

Standards

The hyper storage standard was developed by Sony , Hitachi and 3M . Hyper storage was not widely used.

The GIGAMO standard was developed jointly by Sony and Fujitsu . Fujitsu developed the drives, Sony improved the media.

Diameter
[mm] 		Storage capacity
[MB] 		ISO / IEC ECMA year Remarks
90 128 10090 154 1991
90 230 13963 201 1993
90 385 - 223 1995
90 540, 640 15041 - 1997
90 650 15498 239 1996 Hyper Storage 1
90 1,300 17346 351 2003 Original GIGAMO
90 2,300 22533 353 2004 2.3 GB GIGAMO
130 650 10089 - 1991
130 650 11560 153 1991 only WORM
130 1,000 13481 183 1992
130 1,300 13549 184 1992
130 2000 13842 195 1995
130 2,600 14517 - 1996
130 5,200 15286 - 1999
130 9,100 22092 322 2001

distribution

The distribution of the MO was relatively low over its entire construction period. Except for the NeXTcube (where the MO was used as standard instead of a hard drive), it was mostly either just a transport medium (e.g. in the graphics or medical industry) or a backup medium. In the music sector and in private households, the MO was often used as an additional memory for personal documents or music titles.

The MO is very popular and widespread in its home market of Japan. The last major manufacturer of MO drives - Fujitsu - stopped selling Europe in 2007. MO data carriers are still occasionally available on the Internet in Europe, but the drives required for this are hardly affordable for private individuals. MO drives are still available in Japan.

Succession

In research there have also been approaches for MO media with larger storage volumes, but these have not been developed to the point where they are ready for series production because the storage volume requirements of the users have developed much more rapidly. For many fields of application, significantly larger storage volumes are now required than were in the pipeline at the time in the research laboratories. The manufacturers of MO drives said goodbye and left the market to rewritable storage media using phase change technology (a purely optical recording process), which stagnates at 60 GB with the representative Ultra Density Optical (UDO).

MO technology is now modern again. By changing the carrier material from plastic to a metal plate, which is heated selectively by laser, research has shown that rewritable storage media with capacities of up to 100 TB can be achieved. This successor technology runs under the keyword Heat-assisted magnetic recording (HAMR), and the storage medium is called "HAMR hard disk".

Individual evidence

  1. ↑ International Standard ISO / IEC 10090 . 1992 (English, zip ).
  2. ↑ Standard ECMA-154 . ( [1] [accessed February 8, 2008]).
  3. ↑ International Standard ISO / IEC 13963 . 1995 (English, zip ).
  4. ↑ Standard ECMA-201 . ( [2] [accessed February 8, 2008]).
  5. ↑ Standard ECMA-223 . ( [3] [accessed February 8, 2008]).
  6. ↑ Standard ECMA-239 . ( [4] [accessed February 8, 2008]).
  7. ↑ Hitachi Systems: Hyper Storage 1 (Japanese) . ( [5] [accessed February 8, 2008]). Hitachi Systems: Hyper Storage 1 (Japanese) ( Memento of the original from December 13, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / ew.hitachi-system.co.jp
  8. ↑ International Standard ISO / IEC 17346 . 2005 (English, zip ).
  9. ↑ Standard ECMA-351 . ( [6] [accessed February 8, 2008]).
  10. ↑ Technologies of "GIGAMO" system . ( [7] [accessed February 8, 2008]). Technologies of "GIGAMO" system ( Memento of the original from December 9, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.mo-forum-asia.com
  11. ↑ International Standard ISO / IEC 22533 . 2005 (English, zip ).
  12. ↑ Standard ECMA-353 . ( [8] [accessed February 8, 2008]).
  13. ↑ Fujitsu and Sony Expand GIGAMO Standard to 2.3GB . ( [9] [accessed February 8, 2008]).
  14. ↑ International Standard ISO / IEC 11560 . 1992 (English, zip ).
  15. ↑ Standard ECMA-153 . ( [10] [accessed February 8, 2008]).
  16. ↑ International Standard ISO / IEC 13481 . 1993 (English, zip ).
  17. ↑ Standard ECMA-183 . ( [11] [accessed February 8, 2008]).
  18. ↑ International Standard ISO / IEC 13549 . 1993 (English, zip ).
  19. ↑ Standard ECMA-184 . ( [12] [accessed February 8, 2008]).
  20. ↑ International Standard ISO / IEC 13842 . 1995 (English, zip ).
  21. ↑ Standard ECMA-195 . ( [13] [accessed February 8, 2008]).
  22. ↑ International Standard ISO / IEC 22092 . 2002 (English, zip ).
  23. ↑ Standard ECMA-322 . ( [14] [accessed February 8, 2008]).
  24. ^ Tape media with type: MO. Retrieved March 11, 2017 .
  25. ↑ Tape drives internal with type: MO. Retrieved March 11, 2017 .
  26. ↑ Tape drives external with Type: MO. Retrieved March 11, 2017 .
  27. ↑ More storage space: Seagate has announced HAMR hard drives for the end of 2016. Retrieved August 17, 2015 .

literature

  • Stephan Becker: Fine-grained: Higher storage densities with magneto-optical removable disks . In: c't . tape 15 , no. 25 , 1998, pp. 190–195 ( [15] - subject to a charge. The article presents the technical differences between MOD and DVD-RAM in an understandable and detailed manner.).

Web links

Commons : MO  - album with pictures, videos and audio files