You can seamlessly locate and connect to any service or filesystem that's been registered with the process manager. When a filesystem resource manager registers a mountpoint, the process manager creates an entry in the internal mount table for that mountpoint and its corresponding server ID (i.e., the nd, pid, chid identifiers).
This table effectively joins multiple filesystem directories into what users perceive as a single directory. The process manager handles the mountpoint portion of the pathname; the individual filesystem resource managers take care of the remaining parts of the pathname. Filesystems can be registered (i.e., mounted) in any order.
When a pathname is resolved, the process manager contacts all the filesystem resource managers that can handle some component of that path. The result is a collection of file descriptors that can resolve the pathname.
If the pathname represents a directory, the process manager asks all the filesystems that can resolve the pathname for a listing of files in that directory when readdir() is called. If the pathname isn't a directory, then the first filesystem that resolves the pathname is accessed.
For more information on pathname resolution, see the section “Pathname management” in the chapter on the Process Manager in this guide.