With Unix/Linux CDR it involves loading a device driver and replacing the mount point (from the local device) to a device created by the cdr module that gets loaded into the kernel. This won't work with NFS as NFS is also a module loaded into the kernel, and these will interfere with each other.
This is why (on the source) you see the mount point change from /dev/dsk/xxxxx to /dev/cxbf/cxbfN. It also explains why (during configuration) any applications running on the source path need to be shut down (for the remount of the file system to occur)
The destination can be on an NFS mount because no driver is required for the destination.
Ernst F. Graeler
Senior Engineer III