Comment 5 for bug 1642098

I've updated my installation to duplicity 0.7.13.1+bzr1308 and retested it. The PAR2 files are now generated when I try a test command like this (backing up 22GB of my music):

    duplicity full --verbosity=9 --volsize=5000 --par2-options -m15000 /home/gwern/music/ par2+file:///media/gwern/My\ Book/duplicity2/

The RAM option shows up in the invocation when I watch in htop, memory consumption increases with large volsizes, and par2verify is successful but only if I use a for loop.

---

Looking at the generated par2 files and noting the interleaving of PAR2 with the backup volumes, I am a little confused. It seems that duplicity is not generating a PAR2 for the set of generated volumes, but is generating a single PAR2 for each volume individually? Doesn't this largely defeat the entire point of generating PAR2? If a single volume is lost for any reason, it cannot be repaired using a 10% PAR2 of it on its own, thereby corrupting the entire backup and all incrementals after it; while it could have been repaired if PAR2 was being used normally on the entire set of generated volumes. The only thing that you could repair with per-volume PAR2s would be, I dunno, some bitflips or (very small) amounts of truncation. Am I invoking PAR2 wrong in the duplicity options?