You can recognize a DVD-RAM immediately because visually there are lots of little rectangles distributed on the surface of the data carrier.
DVD-RAM (Digital Versatile Disc –- Random Access Memory) is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD writers. DVD-RAM media are used in computers as well as camcorders and personal video recorders since 1998.
Compared with other DVDs, DVD-RAM is much more similar to a harddisk, as it has concentric tracks instead of one long spiral track. Unlike the competing formats DVD+R, DVD-R, DVD+RW and DVD-RW, you do not need special DVD burning software to write or read DVD-RAMs on a computer. DVD-RAMs can be accessed like a usual floppy disk or hard drive.
See also DVD, Compact Disc.
Since the Internationale Funkausstellung Berlin 2003 the specification is being marketed by the RAM Promotion Group (RAMPRG), built by Hitachi, Toshiba, Maxell, LG Electronics, Matsushita/Panasonic, Samsung and Teac. DVD-RAM is considered a highly reliable format, as the discs have built-in error control. It is a common misconception that DVD-RAM uses magneto-optical (MO) technologies: DVD-RAM is a pure phase change medium.
The specification separates between
- DVD-RAM 1.0
- Single-sided, one layer discs with a capacity of 2.58 GB
- Double-sided one layer discs with a capacity of 5.16 GB
- DVD-RAM 2.0
- Single-sided, one layer discs with a capacity of 4.7 GB
- Double-sided one layer discs with a capacity of 9.4 GB
Physically smaller DVD-RAM discs also exist with a capacity of 1.46 GB, but they are uncommon. DVD-RAMs were originally solely sold in cartridges; recent DVD recorders however also work with no-cartridge discs – some devices even do not support cartridges anymore. A cartridge disc is about 50% more expensive than a disc without cartridge.
Currently there are three competing formats for rewritable DVDs: DVD-RAM, DVD+RW and DVD-RW. DVD-RAM is in particular more suitable for data backups and the use in camcorders than DVD±RW.
Advantages of DVD-RAM compared to the competing formats
- Long durability of minimum 30 years.
- Can be rewritten > 100,000 times (DVD±RW ca. 1,000 times).
- No DVD burning software required in computers – discs can be used and accessed like a removable hard disk.
- Very fast access of smaller files on the disc.
- Automatic hardware verification of written data, no need to run a software verification after the burning finished
- The cartridges make it very handy (where applicable).
- In DVD recorders DVD-RAM is the only removable medium which allows time shifting.
Type 2 does not always come in a case.
- Most DVD recorders do not support DVD-RAM.
- The medium is more expensive than DVD±RW.
- DVD+RW can be written faster than DVD-RAM when writing large amounts of data.
- Official website of the RAM Promotion Group (http://www.ramprg.com)
- Pansonic article about history of DVD-RAM (1973-1998) (http://www.panasonic.com/industrial/computer/storage/dvdram/about/history.htm).