[Duplicity-talk] Duplicity always checks every file

[Giulio Bernardi]

Hello everybody,

I just started using duplicity to back up my home directory: overall, it
consists of about 700,000 files (147 gb). The full backup went just fine, but I
noticed that it takes a lot of time for subsequent incremental backup to just
determine which files are changed.
For example, if I run duplicity with --dry-run, it takes 31 minutes on my (slow)
laptop just to determine which files were changed.
My previous backup strategy was to rsync my home directory to another machine:
if very few files were changed, it completed in less than 1 minute.

Strace shows that duplicity is scanning each subdirectory, performing a lstat()
of every file it finds: is this the expected behaviour or is there something
strange? I would expect that duplicity do not enter directories whose timestamp
did not change since last run (I think this is what rsync does).

I am using 7.12 from fedora: duplicity-0.7.12-1.fc25.x86_64, which seems to be
the plain vanilla version, without any additional patches.

Giulio