Design
There are three competing technologies for rewritable DVD
DVD
DVD, also known as Digital Versatile Disc or Digital Video Disc,is an optical disc storage media format, and was founded in 1995. Its main uses are video and data storage...
s: DVD-RAM, DVD+RW
DVD+RW
DVD+RW is the name of a standard for optical discs: one of several types of DVD, which hold up to about 4.7 GB per disc and are used for storing films, music or...
and DVD-RW
DVD-RW
A DVD-RW disc is a rewritable optical disc with equal storage capacity to a DVD-R, typically 4.7 GB. The format was developed by Pioneer in November 1999 and has been approved by the DVD Forum...
. DVD-RAM is considered a highly reliable format, as the discs have built-in error control and a defect management system. Therefore, DVD-RAM is perceived to be better than the other DVD technologies for traditional computer usage tasks such as general data storage, backup and archival, though the Mount Rainier Format
Mount Rainier (packet writing)
Mount Rainier is a format for writable optical discs which provides the packet writing and defect management. Its goal is the replacement of the floppy disk...
standard for DVD+/-RW (and CD-R, CD-RW, DVD+/-R) somewhat lessens the DVD-RAM format's perceived advantage.
DVD-RAM has a larger presence in camcorders and set-top boxes than in computers, although the popularity of DVD-RAM in these devices can be explained its being very easily written to and erased, which for example allows extensive in-camera editing.
The on-disc structure of DVD-RAMs is closely related to hard disk
Hard disk
A hard disk drive is a non-volatile storage device that stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to the motorized mechanical aspect that is distinct from its medium, such as a tape drive and its tape, or a floppy disk...
and floppy disk
Floppy disk
A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangular plastic shell. Floppy disks are read and written by a floppy disk drive or FDD, the initials of which should not be confused with "fixed disk drive," which...
technology, as it stores data in concentric
Concentric
Concentric objects share the same center, axis or origin with one inside the other. Circles, tubes, cylindrical shafts, disks, and spheres may be concentric to one another...
tracks. DVD-RAMs can be accessed just like a hard or floppy disk and usually without any special software. DVD-RWs and DVD+RWs, on the other hand, store data in one long spiral
Spiral
In mathematics, a spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.-Three-dimensional spirals:...
track and require special packet reading/writing software to read and write data discs. Like magneto-optical (MO) technologies, DVD-RAM has numerous rectangles on the disc surface that define the boundaries of data sectors
Hard sectoring
Hard sectoring in a magnetic or optical data storage device is a form of sectoring which uses a physical mark or hole in the recording medium to reference sector locations....
. However, DVD-RAM is not MO but a phase change medium, similar to CD-RW, DVD-RW, or DVD+RW.