Thanks for help with Linux or Raspi's but I have Linux Ubuntu and now Mint since some years and two more Raspi's for Radio/CD-Player and a TV streaming/saving nice films. The idea was to do a mediacenter with Kodi. But Kodi in my view is rubbish ... ok, coming from the playstation and that all to be said.

Ok, that the timestamp inside a package stays intact is surely right and so usable if safed to the database. But I would make a CRC of the complete package as a first indicator.

Ok, your toughts are much more forward if you want to store the poser files as such (cr2, pz2, ...) in database. These indeed are documents in that sense. But that was/is not my intention. Only the names, types and such should go to DB not the file itself. And so the document approach is far more as what I need. And therefor a crash of the DB (even not such often) will destroy absolutely nothing than information.