Thank you Thorsten.
Adding a few more new volumes has solved a problem - balancing is working now.
We will plan upgrade to 7.9.08.25.
>and, yes, a new file should have been added automatically - any error in the database log file or any >attempt to add a volume visible?
I don't see any logs about automatic adding new volumes to database (it sholud occure at 90% and it was over 91% since one week).