Re: [Duplicity-talk] --skip-same-content: Option to skip files whose content hasn't changed

[Elifarley Callado Coelho Cruz]

Hi Nate,

The point of having a switch like '--skip-same-content' is to suppress
the recording of changed mtimes when the file content hasn't changed.
In some situations, it's not really important to track changes to
mtimes, so why keep recording them?

This will also help with the problem described at
https://bugs.launchpad.net/duplicity/+bug/768481 (Don't write new
incremental set if nothing changed).

Here's an excerpt:

---
For example, a few days ago I needed to restore three small files from
a small backup set that hadn't changed in years. But to do so,
Duplicity had to download probably over a hundred incremental sets in
which nothing changed. This took a LONG time! It's especially slow
since, judging from Duplicity's verbose output, it downloads one file
at a time--the latency between commands adds up quickly (I'm ignorant
about SFTP: is there no way to request more than one file at a time?).
Restoring less than 20 KB of data took over 10 minutes because of all
the empty incremental sets that had to be downloaded.
---

- Elifarley

---

Re: [Duplicity-talk] --skip-same-content: Option to skip files whose con

From:    Nate Eldredge
Subject:         Re: [Duplicity-talk] --skip-same-content: Option to skip
files whose content hasn't changed
Date:    Thu, 24 Nov 2011 16:46:10 -0500 (EST)
On Thu, 24 Nov 2011, Elifarley Callado Coelho Cruz wrote:

It would be nice to have an option to skip files which had their
modification time changed without any changes to their content.

Thanks to the rdiff algorithm, this effectively already happens.
Duplicity only backs up the changes relative to the previous version
of the file. If the data has not changed, it won't be backed up again.
The file will still be entered in the backup (and the new mtime
recorded), but no data will be stored and the size of the backup won't
increase significantly. Try it and see!

--

Nate Eldredge
address@hidden