On Wed, Dec 13, 2023 at 12:48 AM Satoru Takeuchi
<[email protected]> wrote:
>
> Hi Ilya,
>
> 2023年12月12日(火) 21:23 Ilya Dryomov <[email protected]>:
> > Not at the moment. Mykola has an old work-in-progress PR which extends
> > "rbd import-diff" command to make this possible [1].
>
> I didn't know this PR. Thank you very much.I'll evaluate this PR later.
>
> > Since you as
> > a user expected "rbd merge-diff" to be able to this, I wonder if this
> > functionality might be better placed under "rbd merge-diff"? That way
> > the operations on files would be separated from the operations on RBD
> > images.
>
> Yes, I think so too.
>
> >
> > For your backup system, couldn't you just merge the two oldest
> > differentials with "rbd merge-diff" instead? Instead of advancing the
> > full export, you would be advancing the first differential -- it would
> > represent a diff between the initial export and the "2 weeks" backup
> > over time.
>
> Yes, it's possible. It's one of a workaround I thought. Then the
> backup data are as follows:
>
> a. The full backup taken at least 14 days ago.
> b. The latest 14 days backup data
I think it would be:
a. A full backup (taken potentially months ago, exact age doesn't
really matter)
b. Differential #1 - diff from the full backup to the 14 days old version
c. Differential #2 - diff from the 14 days old to the 13 days old version
d. Differential #3 - diff from the 13 days old to the 12 days old version
...
Every day after a new differential is taken, (b) and (c) would be
merged, keeping the number of differentials constant.
>
> In this case, I concern the effect if (a) becomes too old. However, it
> might be a groundless fear.
I would suggest re-capturing the full backup from time to time, just as
a precaution against something going wrong with a backup based on a too
long series of (merged) differentials. It might be groundless concern,
but then you can't be too careful when it comes to backups.
Thanks,
Ilya
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