[Borgbackup] lzma, 3-2-1 rule

[Thorsten Schöning]

Guten Tag Boris Kirkorowicz,
am Freitag, 31. März 2023 um 11:36 schrieben Sie:

> This is new to me, maybe I overlooked something when choosing "-C
> lzma,9".

You most likely missed the following warning:

> Giving levels above 6 is pointless and counterproductive because it
> does not compress better due to the buffer size used by borg - but
> it wastes lots of CPU cycles and RAM.

https://manpages.debian.org/testing/borgbackup/borg-compression.1.en.html

> So should I stop backing up using lzma and start again with an other
> compression method, or is it safe to continue?

I don't think that reading LZMA will be removed too soon, using it for
new data might be. OTOH, different compression methods can be mixed
freely, so you don't need to care too much:

> It is no problem to mix different compression methods in one
> repo[...]

https://manpages.debian.org/testing/borgbackup/borg-compression.1.en.html

There was a thread recently about compression performance, regarding
that you should definitely stop using LZMA for performance reasons.

https://mail.python.org/pipermail/borgbackup/2023q1/002165.html

> Second question: the article says that it is no good idea to
> fulfill the 3-2-1 rule by copying the borg repositories, since
> errors might be copied. This sounds plausible, but on the other hand
> it would multiply the time of backup. In my case it could take more
> than one year, so I wonder how to do this. Any advice how to handle this?

Don't waste backup time with LZMA anymore and run multiple individual
backups to different repos one after another. Besides that and
depending on the performance of your source system, you might run
multiple BORG processes concurrently as long as they use different
target repos. If I remember correctly you discussed that for your
initial backup yourself already.

Mit freundlichen Grüßen

Thorsten Schöning

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