On Fri, 24 Apr 2020, MRob via Duplicity-talk wrote:
Hello, I want to ask opinion about backup tactic please.
I found a backup system that using only rsync to a local server. A few
scripts run on the server that create tree of historical directrories
that are filled with hard links to the main rsync target. I never saw
this but my understand of the benefit:
* saving space for historical backups because they only use inodes
* simple scheme to use rsync and ln
* But am I correct, to understand if a file *change* then the
historical data is lost so its a shortcoming of the scheme.
Well, it could work either way. Maybe it only keeps the latest
version of files that change, maybe it keeps all past versions. I
can't tell from your description alone. It'd help if you would
provide a link to the system you are talking about.
Duplicity uses the rdiff algorithm to only track the changes in a
file's contents. So if you have a 1 GB file and you add 1 KB,
duplicity will only need an additional 1 KB (or so) to make an
incremental backup of that file, and you only use a total of 1 GB + 1
KB of backup storage, while maintaining the ability to recover either
the old or the new version. With the system you describe, it sounds
like either you lose the old version, or you use 2 GB of backup
storage.