[Borgbackup] The size of a upgraded Attic repository is almost doubled

[Thomas Waldmann]

> while converting an old Attic repository, and after the first Borg
> backup, I noticed that the size of the whole repository was almost
> doubled.

That is expected, search the docs / faq for --chunker-params for an
explanation.

> I suspect that what is happening is that Borg is simply storing the
> old Attic backups, but since new ones use a different algorithm, they
> cannot share data blocks, thus the increase in size.

Same algorithm, but different parameters.

> I am not particularly worried about this, since I will eventually
> prune the old backups

Yes. And likely you will want to go that route.

>, but I wanted to know if I am right, in order to
> account enough space for future upgrades of other Attic repositories I
> have.

You can avoid the repo size doubling by using attic-compatible chunker
params.

But that will have a negative impact on resource usage then (and long
term), so maybe rather don't do that.


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