[Borgbackup] Repo sync efficiency

[Thomas Waldmann]

> I've tried to sync my borg repo to cloud storage after each time I
> create a borg archive. But my observation is that even with a small
> change on destination borg repo still changes alot in term of number of
> files changed (under data/ folder) not total size of repo and in result
> I need a large transmitted data. This is a example:
> 
> - Borg output:
> 
>                  Original size      Compressed size    Deduplicated size
> This archive:          3.24 MB              1.89 MB             70.14 kB
> All archives:         17.77 MB             13.31 MB              9.96 MB
> 
>                  Unique chunks         Total chunks
> Chunk index:              1548                 2022
> 
> 
> - 'rclone sync' (to sync my borg repo and google drive) output:
> 
> Transferred:   9.721 MBytes (564.116 kBytes/s)
> Transferred:            6
> 
> Is there anything I can do about it?

This might be partly due to compact_segments, which is run automatically
at the end of all major repo-writing activities. It will delete
non-compact segment files and create new compact segment files.

Guess you'ld see less changes with a repo in append-only mode, but OTOH
that repo would always grow while being in that mode.

Also, borg 1.1 might do less compaction if it decides it is not worth
the effort. OTOH, borg 1.1 has way bigger segment files by default if
you init a repo with it.

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