Eli,

I think you are now halfway there.  Let's think.  First you need to
also run and understand a bit the coda backup program (backup).  This
program goes through the dumplist (ask Henry how to set that right)
and does cloning, and - possibly incremental - dumping on all the volumes
in the dumplist.

BTW I asked the secretary Lesa here to mail the paper on backups to
Bradley, somehow I lost the mailing address you gave me. It describes
the dumplist and the "ancient" files. 

Try to run backup (Henry will help you) and then read the code in
backup.cc and the vol-dump.cc and related files.  This will show you
what to modify, but I'd like to see a bit of planning before the
hacking starts so that we end up with the right kind of ideas in the
backup code.

- Peter -