[Borgbackup] Central backup and ~/.cache/borg/ piling up

[Bzzzz]

On Sun, 30 Aug 2020 13:48:36 +0200
Hans-Peter Jansen <hpj at urpla.net> wrote:

> Guess, the sheer amount is due to many vm images and some such.

Ah, in this case you wanna fiddle with --chunker-params to lower the
chunk size to avoid almost the whole image file to be backed up when
there are little changes.

From what I read onzeweb, my notes say:
* ORG is 					: 19,23,21,4095

* a pro with lots of VM images fixed it to 	: 16,23,11,4095
    and say it's doing the trick

* a rookie fixed it to				: 12,20,15,4095
    but this seems too low and multiplies BB files

* I fixed it to					: 16,23,16,4095
    and it seems to work correctly with heavy VBox images (essentially
    of the windo$e kind)

Note that it won't change big things if you're at 90% writing in these or
worse, you defragment them (w$).

> This is going to strive towards some prune implied limit, sure, but
> those 20G already caused me some headaches on certain systems and will
> slowly raise still (due to monthly retentions).

May be (if possible) you could separate the VM images backup from the
rest, using a low 3rd parm for --chunker-params for VMs - but before
that, you have to be sure it is them who inflate the account list.

"borg diff" is your friend to know where the bloat is located, because it
provides you the old/new backup file sizes differences - it may take a
moment to analyze it's output, but this way you'll be sure of the bloat
source (you might have surprises…;)

Jean-Yves