A DVD-RW disc is a rewritable optical disc with equal storage capacity to a DVD-R, typically 4.7 GB (4,700,000,000 bytes). The format was developed by Pioneer in November 1999 and has been approved by the DVD Forum. The smaller Mini DVD-RW holds 1.46 GB, with a diameter of 8 cm.The primary advantage of DVD-RW over DVD-R is the ability to erase and rewrite to a DVD-RW disc. According to Pioneer, DVD-RW discs may be written to about 1,000 times before needing replacement . DVD-RW discs are commonly used to store data in a non-volatile format, such as when creating backups or collections of files. They are also used for home DVD video recorders. One benefit to using a rewritable disc is if there are writing errors when recording data, the disc is not ruined and can still store data by erasing the faulty data.One competing rewritable format is DVD+RW. Hybrid drives that can handle both, often labeled "DVD±RW", are very popular due to the lack of a single standard for recordable DVDs.The recording layer in DVD-RW and DVD+RW is not an organic dye, but a special phase change metal alloy, often GeSbTe. The alloy can be switched back and forth between a crystalline phase and an amorphous phase, changing the reflectivity, depending on the power of the laser beam. Data can thus be written, erased and re-written.