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From: Siraj G <tosiraj.g@gmail.com>
Date: Thu, 20 Mar 2025 18:28:32 +0530
Message-ID: <CAC5iy60NgOv2nRYNwSh2n-Pj82eUjghgWjV2VCuQUABsAZ9uiw@mail.gmail.com>
Subject: Re: Export operation efficiency in read replica
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: pgsql-general@lists.postgresql.org
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Hello Laurenz

As per my understanding coming to a proper conclusion wrt RPO with export
operation is challenging. Eg., the export started at x and ended at z, the
time stamp here for many data sets is different. Moreover, I do not think
there is an incremental way available for export, correct?

Please correct me if my understanding is wrong.

Although I do agree the primary choice of backup to be storage based, we
wanted to have export backups as well as a secondary.

Concerning the impact taking export on read only.. Would you think we may
run into recovery issues on the replica side or anything that would prevent
the operation from being successful?

Regards
Siraj

On Thu, Mar 20, 2025 at 5:29=E2=80=AFPM Laurenz Albe <laurenz.albe@cybertec=
.at>
wrote:

> On Thu, 2025-03-20 at 17:22 +0530, Siraj G wrote:
> > I have a DB with 1TB in size serving needs of one of our critical
> > applications. I have a requirement to take export of the DB on a
> > daily basis, but want to carry out this operation in read replica.
> > The postgresql version is: 16.6
> >
> > What would be the RPO of such backup?
>
> Depends on the speed of disk and network and on what an RPO is.
>
> > What would be the impact on the READ REPLICA with a long running
> > export operation?
>
> Potentially severe.
>
> You could look into storage technologies that allow you to take
> a snapshot and clone it.
>
> Yours,
> Laurenz Albe
>

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<div dir=3D"ltr">Hello Laurenz<div><br></div><div>As per my understanding c=
oming to a proper conclusion wrt RPO with=C2=A0export operation is challeng=
ing. Eg., the export started at x and ended at z, the time stamp here for m=
any data sets is different. Moreover, I do not think there is an incrementa=
l way available for export, correct?</div><div><br></div><div>Please correc=
t me if my understanding is wrong.</div><div><br></div><div>Although I do a=
gree the primary choice of backup to be storage based, we wanted to have ex=
port backups as well as a secondary.=C2=A0</div><div><br></div><div>Concern=
ing the impact taking export on read only.. Would you think we may run into=
 recovery issues on the replica side or anything that would prevent the ope=
ration from being successful?</div><div><br></div><div>Regards</div><div>Si=
raj</div></div><br><div class=3D"gmail_quote gmail_quote_container"><div di=
r=3D"ltr" class=3D"gmail_attr">On Thu, Mar 20, 2025 at 5:29=E2=80=AFPM Laur=
enz Albe &lt;<a href=3D"mailto:laurenz.albe@cybertec.at">laurenz.albe@cyber=
tec.at</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"m=
argin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left=
:1ex">On Thu, 2025-03-20 at 17:22 +0530, Siraj G wrote:<br>
&gt; I have a DB with 1TB in size serving needs of one of our critical<br>
&gt; applications. I have a requirement to take export of the DB on a<br>
&gt; daily basis, but want to carry out this operation in read replica.<br>
&gt; The postgresql version is:=C2=A016.6<br>
&gt; <br>
&gt; What would be the RPO of such backup?<br>
<br>
Depends on the speed of disk and network and on what an RPO is.<br>
<br>
&gt; What would be the impact on the READ REPLICA with a long running<br>
&gt; export operation?<br>
<br>
Potentially severe.<br>
<br>
You could look into storage technologies that allow you to take<br>
a snapshot and clone it.<br>
<br>
Yours,<br>
Laurenz Albe<br>
</blockquote></div>

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