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

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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