I think what you are describing is a feature of the Amanda backup system, which might be worth a look. It supports writing to a library of "virtual tapes" which

I think what you are describing is a feature of the Amanda backup system, which might be worth a look. It supports writing to a library of "virtual tapes" which can then be backed by real tapes, tape libraries, hard disks, etc. and will handle the splitting/overflow problem that you are dealing with. https://www.zmanda.com/downloads/ https://www.zmanda.com/downloads/