Disc spanning is a feature of CD and DVD burning software that automatically distributes a large data set across multiple optical discs when the total size exceeds the storage capacity of a single blank disc. The primary advantage is that the user does not need to manually split files and directories into disc-sized portions.
Overview
Disc spanning software handles the distribution of data across multiple discs. The software may or may not support splitting a single large file across multiple discs, but all disc spanners can divide numerous files that are each smaller than one disc's capacity across a set of discs.
Some disc spanning schemes include a small program written to the first disc (or to every disc in the set) that reassembles the data set into its original structure on the target machine.
Reliability
Disc spanning works well on CD media in many applications, but spanning on DVD media has historically been less reliable. This is notable because disc spanning was used extensively on older 3.5-inch and 5.25-inch floppy disks. Contrary to common assumption, most operating systems do not include built-in disc spanning functionality for optical media.
Limitations
Using disc spanning typically makes the files unreadable to the standard file system, meaning the same software must be used later to restore the data. Because of this dependency, some users prefer "simple disc spanning" instead.
Simple Disc Spanning
Simple disc spanning groups files into media-sized sets based on total size, without splitting individual files. The drawback is that any single file larger than the target media capacity will not be written. It provides a straightforward calculation of how many discs a given collection of files requires.
Related Concepts
- Spanned volume – A similar concept for hard disk drives, where data is stored across multiple physical disks but appears as a single volume.
- File spanning – The ability to package a single file or data stream into separate files of a specified size.
