The CDA is a 6 byte binary number used to identify a node frame in a node pot, a node pot itself, or a page.
The CDA is purely a kernel construct.
A CDA can be transformed into a physical disk address with a little arithmetic and a small set of tables of ranges.
When a disk is mounted the kernel reads a table of ranges from the disk that announce which CDAs are on this disk.
Each range is some substantial portion of the disk.
A range is expected to live on more than one disk for purposes of redundancy.
Extensive cross checks are in place to ensure that at least one copy of
a range is accessible.
When a disk is introduced with obsolete ranges a process is begun to repair that range.
See about range keys and CDA’s.
See prepared keys and CDA’s.