Most CDs and DVDs are formatted to the ISO 9660 standard, which is portable. So, most CDs and DVDs can be mounted by volume management. However, CDs or DVDs with UFS file systems are not portable between architectures. So, they must be used on the architecture for which they were designed.
For example, a CD or DVD with a UFS file system for a SPARC platform cannot be recognized by an x86 platform. Likewise, an x86 UFS CD cannot be mounted by volume management on a SPARC platform. The same limitation generally applies to diskettes. However, some architectures share the same bit structure, so occasionally a UFS format specific to one architecture will be recognized by another architecture. Still, the UFS file system structure was not designed to guarantee this compatibility.
To accommodate the different formats, the CD or DVD is split into slices. Slices are similar in effect to partitions on hard disks. The 9660 portion is portable, but the UFS portion is architecture-specific. If you are having trouble mounting a CD or DVD, particularly if it is an installation CD or DVD, make sure that its UFS file system is appropriate for your system's architecture. For example, you can check the label on the CD or DVD.