Just brainstorming here, based on our recent purchase of an RMS docking
station, which has 1.5 TB capacity, and uses an "optical" file system.
Rather than saving to tape, what if you used a "copy" command to save only
"new" or "changed" stream files since the last "copy" process. The command
might use a database table to store the attributes of IFS objects, so the
command might know which objects are *new or *changed.
You may need to upgrade to Power 7 or 8, however.