| DVD-RAM (DVD–Random Access Memory) is | | | | |
| a disc specification presented in 1996 by the | | | | Advantages of DVD-RAM |
| DVD Forum, which specifies rewritable DVD-RAM | | | | |
| media and the appropriate DVD writers. | | | | Long life — without physical damage, |
| DVD-RAM media have been used in computers as | | | | data is retained for 30 years minimum. |
| well as camcorders and personal video | | | | |
| recorders since 1998. | | | | Can be rewritten over 100,000 times |
| | | | (DVD±RW can be rewritten approx. 1,000 |
| Currently there are three competing | | | | times). Faster DVD-RAMs support fewer |
| technologies for rewritable DVDs: DVD-RAM, | | | | rewrites (3x speed: 100,000, 5x speed: |
| DVD+RW and DVD-RW. DVD-RAM is considered a | | | | 10,000), but still more than DVD±RW. |
| highly reliable format, as the discs have | | | | (Remember, these are theoretical numbers. In |
| built-in error control and a defect | | | | practice they could be smaller depending on |
| management system. Therefore, DVD-RAM is | | | | the drive, the treatment of the disc and the |
| perceived to be better than the other DVD | | | | file system.) |
| technologies for traditional computer usage | | | | |
| tasks such as general data storage, backup | | | | Reliable writing of discs. Verification done |
| and archival, though the Mt. Rainier standard | | | | in hardware by the drive, so post-write |
| for DVD+RW lessens this somewhat. Curiously, | | | | verification by software is unnecessary. |
| DVD-RAM has a larger presence in camcorders | | | | |
| and set-top boxes than in computers, although | | | | Disc defect management safeguards data. |
| the DVD-RAM's popularity in these devices can | | | | |
| be explained by the fact that it is very | | | | Write speed twice as fast (when verification |
| easily written to and erased, which for | | | | not enabled) as DVD±RW. (Note: 12x DVD-RAM |
| example allows extensive in-camera editing. | | | | spec = 16 DVD±RW spec. As of 7/24/06, |
| | | | DVD±RW write speed was at 8x (DVD±RW |
| The on-disc structure of DVD-RAMs is closely | | | | specifications) while DVD-RAM is at 12x |
| related to hard disk and floppy disk | | | | (DVD-RAM speed specification).) |
| technology, as it stores data in concentric | | | | |
| tracks. DVD-RAMs can be accessed just like a | | | | DVD-burning software may not be required |
| hard or floppy disk and usually without any | | | | — discs can be used and accessed like |
| special software. DVD-RWs and DVD+RWs, on the | | | | a removable hard disk. Mac OS (8.6 or later) |
| other hand, store data in one long spiral | | | | supports DVD-RAM directly. Windows XP |
| track and require special packet reading | | | | supports DVD-RAM directly only for |
| writing software to read and write data | | | | FAT32-formatted discs. Device drivers or |
| discs. It is a common misconception that | | | | other software are needed for earlier |
| DVD-RAM uses magneto-optical (MO) | | | | versions of Windows or if one wants to use |
| technologies: DVD-RAM is a pure phase change | | | | the decidedly better UDF format rather than |
| medium, similar to CD-RW or DVD-RW | | | | FAT32. |
| | | | |
| Many operating systems like Mac OS (Mac OS | | | | Easier to use than other DVD technology. |
| 8.6 or later), Linux and Microsoft Windows XP | | | | |
| support DVD-RAM operation directly, while | | | | Very fast access of smaller files on the |
| earlier versions of Windows require device | | | | disc. |
| drivers or the program InCD. The optical | | | | |
| drives shipped with most Apple Macintosh | | | | 2 KB disc block size wastes less space when |
| computers do not support DVD-RAM operation, | | | | writing small files. |
| but a third party DVD-RAM-compatible drive | | | | |
| can be connected and used directly with Mac | | | | Finalization not necessary. |
| OS. | | | | |
| | | | Media available with or without protective |
| Windows XP can only write directly to FAT32 | | | | cartridges. |
| formatted DVD-RAM discs. For UDF formatted | | | | |
| discs, which are considered faster, | | | | In video recorders, DVD-RAM can be written to |
| compatible device drivers or software such as | | | | and watched (even separate programs) at the |
| InCD or DLA are required. Windows Vista can | | | | same time, much like TiVo. |
| natively access and write to UDF formatted | | | | |
| DVD-RAM discs. This is a non-issue with Linux | | | | Supports time slip recording and recording |
| however, which allows the use of virtually | | | | without border in/out writing. |
| any file system of the multitude that ship | | | | |
| with the operating system, including UDF. Mac | | | | Disadvantages of DVD-RAM |
| OS can read and write HFS, HFS Plus, FAT and | | | | |
| UDF formatted DVD-RAM discs directly. It is | | | | Less compatibility than DVD+RW and DVD-RW (as |
| even possible to use the ext3 file system on | | | | noted above). |
| a DVD-RAM disc. So while it is possible to | | | | |
| use any filesystem one likes, only very few | | | | 12x media is not readily available in the USA |
| perform well on DVD-RAM. This is because some | | | | and will not be available in the US and |
| file systems frequently over-write data on | | | | Europe in the near future due to low market |
| the disc and the table of contents is | | | | demand. 16x media may not be available |
| contained at the start of the disc. | | | | anywhere except manufacturers' R&D |
| | | | laboratories. |
| Many DVD standalone players and recorders do | | | | |
| not support DVD-RAM, especially older or | | | | DVD-RAM media is more expensive than other |
| cheaper versions. However, within the | | | | DVD types. 12x media is expected to cost |
| "RAMPRO" (DVD RAM promotion) group are a | | | | almost $9 per disc, at least initially, but |
| number of well-known manufacturers of | | | | this price will fall as production ramps up. |
| standalone players and recorders that DO | | | | |
| support DVD-RAM. Panasonic for instance have | | | | DVD-RAM writing will be slower than DVD+RW |
| a range of players and recorders which make | | | | and DVD-RW until 12x DVD-RAM media becomes |
| full use of the advantages of DVD-RAM. There | | | | available. If write verification is enabled, |
| are also a number of video cameras that use | | | | the writing speed is decreased by about half. |
| DVD-RAM as the recording media. | | | | Using FAT32 instead of UDF may also slow |
| | | | DVD-RAM performance. |
| Evaluation | | | | |