On Fri, Sep 10, 2021 at 2:37 PM David Gasaway <[email protected]> wrote:

>
>
> On Thu, Sep 9, 2021 at 2:57 AM Amos T <[email protected]> wrote:
>
>
>> So in that case my a safely assume when borgbackup checks for data
>> modification, the
>> file in question is not downloaded ?  Because in that case, my backup
>> will generate a lot of traffic...
>>
>
> The documentation for `borg create` explains the methodologies for
> detecting changed files.  Basically, with the defaults, it caches the
> metadata of the files it backed up, into a local borg cache.  It doesn't
> even need to read anything at all from the destination (s3ql) file system
> so long as the cache is intact.  If this cache is lost or corrupt, borg has
> to read (download, in the case of s3ql) the entire repository to rebuild
> the cache.
>

I may have to take some of that back.  It sounds like borg does keep
components of the cache on the remote file system.  So a local cache
rebuild doesn't need to download the whole repository.  `borg check`
operations frequently do, however.  The point I was trying to make is,
under normal circumstances, only the local cache is used for change
detection.

-- 
-:-:- David K. Gasaway
-:-:- Email: [email protected]

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