[Borgbackup] Recreate segments after changing max_segment_size

[Sebastian Felis]

On 1/14/21 7:12 PM, Thomas Waldmann wrote:
>> e.g. given sements 0, 1, 2, 3 will be concatenated to segement 0
>>
>> tail -c +9 data/0/1 >> data/0/0
>> tail -c +9 data/0/2 >> data/0/0
>> tail -c +9 data/0/3 >> data/0/0
>> rm data/0/[123]
>> rm hints.* index.* integrity.*
>
> A borg repo is not supposed to be used like that.
>
> Also, I don't think anyone wants to support dealing with a borg repo 
> on that level - at least not me. :-)
>
>> Is there any risk doing this?
>
> The risk is that you accidentally damage your repo, lose data, cause 
> inconsistencies. The other risk is that other people read this and try 
> this (maybe less carefully / knowledgeable than you).

For sure, it is a low level operation with I-know-what-I-do attitude 
covered by a backup of the backup.

And your answers don't say any no-s ;-)

>>> I have several borg repos with small segment sizes of 5 MB. I would 
>>> like
>>> to recreate the segments to a larger size for better repo backup with
>>> rsync/rclone.
>
> Why should it be "better" with a larger size?
>
> The 500MiB default of borg 1.1.x is primarily optimized for local repos.
>
> Doing some sync-to-remote could rather improve by using a 
> smaller-than-default segment size.
I target 128MiB segment sizes for "better" remote backups. 128MiB is 
more a gut decision than a technical evaluated optimum.


Thank you for your answers

Sebastian