Universal Disk Format (UDF) is a file system specification defined by OSTA. One objective of UDF is to replace the ISO9660 file system on optical media (CDs, DVDs, etc). It is also a good file system to replace FAT on removable media.
Any removable media (CD, DVD, flash drive, external hard drive, etc) needs a file system format. Ideally, this format should have these characteristics:
UDF is the only file system that meets all these standards, since it was designed for the information exchange purpose.
- Large partition size (maximum 2TB with 512B block size, or 8TB with 2KB block size)
- 64-bit file size
- Extended attributes (e.g., named streams, or forks) without size limitation
- Long file names (maximum 254 bytes, any character can appear in the name)
- Unicode encoding of file names
- Sparse file
- Hard links
- Symbolic links
- Metadata checksum
- Metadata redundancy (optional in UDF 2.50 or later in metadata partition)
- Defect management (for media that does not manage defect internally, such as CD-RW, DVD-RW, and DVD+RW)