Re: Have you considered using the "multiple data files" mode of par2?

still, per duplicity file (volume, manifest etc.) put on/got from the backend.

see source
  https://gitlab.com/duplicity/duplicity/-/blob/dev/duplicity/backends/par2backend.py?ref_type=heads#L147-176

looks like additional volumes help to repair corrupted files.

..sunny regards ede

On 07.10.2024 16:04, Jasmin68k via Duplicity-talk wrote:
> The number of par2 files is configurable (default: 1) with the --par2-volumes option btw.
>
>> one *parity file per file that is put* on the backend
>>
>> On 07.10.2024 15:36, edgar.soldin--- via Duplicity-talk wrote:
>>> hey Jacob,
>>>
>>> i'm sure par2-backend only uses the one parity file tat is put on the backend. what are you hinting at?
>>>
>>> sunny regards ..ede
>>>
>>> On 07.10.2024 15:22, Jakob Bohm via Duplicity-talk wrote:
>>>> Dear Duplicity backup format designer,
>>>>
>>>> According to the par2 man page (at least on Debian 12), the par2 command
>>>> has two distinct operating modes.  One mode creates one or more small
>>>> parity files for a single data file stored on an imperfect medium or
>>>> service.  The other, processes a group of N data files (such as
>>>> Duplicity volumes) to produce a few shared parity files.  This second
>>>> mode is described in the man page under the subheading "CREATING PAR2
>>>> FILES FOR MULTIPLE DATA FILES" .
>>>>
>>>> Switching to the "multiple data files" mode constitutes a change in
>>>> the backup format and thus needs to be guarded with appropriate
>>>> compatibility logic in order to restore backups made with either
>>>> method, even from damaged storage (where par2 files are actually
>>>> needed) .  To keep a desired robustness level and a manageable temp
>>>> volume size on the client, it is probably necessary to set an internal
>>>> limit on the number of volumes for each par2 run .  For example if
>>>> that limit is 99, the temp volume needs to store about 100 times the
>>>> volume size even if not pipelining the creation of later volumes in
>>>> parallel with par2 processing and upload.
>>>>
>>>> Enjoy
>>>>
>>>> Jakob
>>>
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