Packet Writing

Dennis Faas's picture

Packet writing is a technique used to allow writeable CD-ROM and DVD-ROM media to be used in a similar manner to a floppy disk.

Packet writing can be used both with write-once read-many (WORM media) such as CD-R, DVD+R and DVD-R, and also with rewriteable media such as CD-RW, DVD+RW and DVD-RW. WORM media, however, cannot recover space once it is written to the disc; furthermore, a deleted file does not free space on the disk, and a modified or overwritten file occupies additional space even if the file size has not increased. When the free space on a once-writeable disk is exhausted, no further update to the disk is possible. Rewriteable media, on the other hand, can be updated and reformatted many times just like a floppy disk, limited only by the eventual failure of the media.

Several competing and incompatible packet writing disk formats have been developed, notably those of Adaptec DirectCD and Nero AG InCD. Proposed standards include Universal Disk Format and its proposed extension Mount Rainier. This is further complicated by the fact that is nearly impossible to "unformat" a disc formatted specifically for packet writing, thus rending it unusable in computers that do not have support for the proprietary mode.

UDF (Universal Disk Format) and Packet Writing

UDF is a file system used for optical media, developed by the Optical Storage Technology Association (OSTA), UDF was designed for read-write interoperability among all the major operating systems, as well as compatibility between rewritable and WORM media (write-once read-many).

DVDs discs are largely based on the UDF file system, but the UDF format can also be used in conjunction with CD-Rs and CD-RWs discs. UDF is widely associated with "packet writing" software because rewriteable CDs and DVDs rely on UDF and packet writing to make them function as an extended hard drive (such that you can record and erase files at whim).

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