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